Bug: [FEATURE]: [NMI] Currency Unit Conversion



### :memo: Feature Description

- Each currency can be described in terms of base or minor units. 
- For instance, when dealing with USD currency, the Cent is considered as the minor unit, while the Dollar is considered the base unit. 
- In Hyperswitch, the amount value is expected to be always provided in minor units. 
- For example: In USD, If the amount is 1 in base unit (Dollar), then it will be equivalent to 100 in minor units (Cent)
- Some of the connectors integrated require the amount to be converted to a desirable unit before being passed to them. 
- We have functions `to_currency_base_unit` and `to_currency_lower_unit` in place to convert the minor unit amount to its decimal equivalent and vice versa. These conversions are handled explicitly based on the connector.


### :hammer: Possible Implementation

- ConnectorCommon trait have been implemented for the connector. 
- This trait contains `get_currency_unit` method. This method needs to be implemented. 
- It will define what type of conversion needs to be done during `connector_router_data` creation. Concurrently handle the creation of `connector_router_data` to be passed for the connector request body creation.
- You can check this PR for further reference https://github.com/juspay/hyperswitch/pull/2196

:bookmark: Note: All the changes needed should be contained within `hyperswitch/crates/router/src/connector/`

### :package: Have you spent some time checking if this feature request has been raised before?

- [X] I checked and didn't find a similar issue

### :package: Have you read the Contributing Guidelines?

- [X] I have read the [Contributing Guidelines](https://github.com/juspay/hyperswitch/blob/main/docs/CONTRIBUTING.md)

### :sparkles: Are you willing to submit a PR?

diff --git a/crates/router/src/connector/nmi.rs b/crates/router/src/connector/nmi.rs
index cdeb9c99d5e..4f7ee15d730 100644
--- a/crates/router/src/connector/nmi.rs
+++ b/crates/router/src/connector/nmi.rs
@@ -58,6 +58,10 @@ impl ConnectorCommon for Nmi {
         "nmi"
     }
 
+    fn get_currency_unit(&self) -> api::CurrencyUnit {
+        api::CurrencyUnit::Base
+    }
+
     fn base_url<'a>(&self, connectors: &'a settings::Connectors) -> &'a str {
         connectors.nmi.base_url.as_ref()
     }
@@ -210,7 +214,13 @@ impl ConnectorIntegration<api::Authorize, types::PaymentsAuthorizeData, types::P
         &self,
         req: &types::PaymentsAuthorizeRouterData,
     ) -> CustomResult<Option<types::RequestBody>, errors::ConnectorError> {
-        let connector_req = nmi::NmiPaymentsRequest::try_from(req)?;
+        let connector_router_data = nmi::NmiRouterData::try_from((
+            &self.get_currency_unit(),
+            req.request.currency,
+            req.request.amount,
+            req,
+        ))?;
+        let connector_req = nmi::NmiPaymentsRequest::try_from(&connector_router_data)?;
         let nmi_req = types::RequestBody::log_and_get_request_body(
             &connector_req,
             utils::Encode::<nmi::NmiPaymentsRequest>::url_encode,
@@ -351,7 +361,13 @@ impl ConnectorIntegration<api::Capture, types::PaymentsCaptureData, types::Payme
         &self,
         req: &types::PaymentsCaptureRouterData,
     ) -> CustomResult<Option<types::RequestBody>, errors::ConnectorError> {
-        let connector_req = nmi::NmiCaptureRequest::try_from(req)?;
+        let connector_router_data = nmi::NmiRouterData::try_from((
+            &self.get_currency_unit(),
+            req.request.currency,
+            req.request.amount_to_capture,
+            req,
+        ))?;
+        let connector_req = nmi::NmiCaptureRequest::try_from(&connector_router_data)?;
         let nmi_req = types::RequestBody::log_and_get_request_body(
             &connector_req,
             utils::Encode::<NmiCaptureRequest>::url_encode,
@@ -491,7 +507,13 @@ impl ConnectorIntegration<api::Execute, types::RefundsData, types::RefundsRespon
         &self,
         req: &types::RefundsRouterData<api::Execute>,
     ) -> CustomResult<Option<types::RequestBody>, errors::ConnectorError> {
-        let connector_req = nmi::NmiRefundRequest::try_from(req)?;
+        let connector_router_data = nmi::NmiRouterData::try_from((
+            &self.get_currency_unit(),
+            req.request.currency,
+            req.request.refund_amount,
+            req,
+        ))?;
+        let connector_req = nmi::NmiRefundRequest::try_from(&connector_router_data)?;
         let nmi_req = types::RequestBody::log_and_get_request_body(
             &connector_req,
             utils::Encode::<nmi::NmiRefundRequest>::url_encode,
diff --git a/crates/router/src/connector/nmi/transformers.rs b/crates/router/src/connector/nmi/transformers.rs
index 582bb9f7367..995341fefd9 100644
--- a/crates/router/src/connector/nmi/transformers.rs
+++ b/crates/router/src/connector/nmi/transformers.rs
@@ -40,6 +40,37 @@ impl TryFrom<&ConnectorAuthType> for NmiAuthType {
     }
 }
 
+#[derive(Debug, Serialize)]
+pub struct NmiRouterData<T> {
+    pub amount: f64,
+    pub router_data: T,
+}
+
+impl<T>
+    TryFrom<(
+        &types::api::CurrencyUnit,
+        types::storage::enums::Currency,
+        i64,
+        T,
+    )> for NmiRouterData<T>
+{
+    type Error = Report<errors::ConnectorError>;
+
+    fn try_from(
+        (_currency_unit, currency, amount, router_data): (
+            &types::api::CurrencyUnit,
+            types::storage::enums::Currency,
+            i64,
+            T,
+        ),
+    ) -> Result<Self, Self::Error> {
+        Ok(Self {
+            amount: utils::to_currency_base_unit_asf64(amount, currency)?,
+            router_data,
+        })
+    }
+}
+
 #[derive(Debug, Serialize)]
 pub struct NmiPaymentsRequest {
     #[serde(rename = "type")]
@@ -77,25 +108,27 @@ pub struct ApplePayData {
     applepay_payment_data: Secret<String>,
 }
 
-impl TryFrom<&types::PaymentsAuthorizeRouterData> for NmiPaymentsRequest {
+impl TryFrom<&NmiRouterData<&types::PaymentsAuthorizeRouterData>> for NmiPaymentsRequest {
     type Error = Error;
-    fn try_from(item: &types::PaymentsAuthorizeRouterData) -> Result<Self, Self::Error> {
-        let transaction_type = match item.request.is_auto_capture()? {
+    fn try_from(
+        item: &NmiRouterData<&types::PaymentsAuthorizeRouterData>,
+    ) -> Result<Self, Self::Error> {
+        let transaction_type = match item.router_data.request.is_auto_capture()? {
             true => TransactionType::Sale,
             false => TransactionType::Auth,
         };
-        let auth_type: NmiAuthType = (&item.connector_auth_type).try_into()?;
-        let amount =
-            utils::to_currency_base_unit_asf64(item.request.amount, item.request.currency)?;
-        let payment_method = PaymentMethod::try_from(&item.request.payment_method_data)?;
+        let auth_type: NmiAuthType = (&item.router_data.connector_auth_type).try_into()?;
+        let amount = item.amount;
+        let payment_method =
+            PaymentMethod::try_from(&item.router_data.request.payment_method_data)?;
 
         Ok(Self {
             transaction_type,
             security_key: auth_type.api_key,
             amount,
-            currency: item.request.currency,
+            currency: item.router_data.request.currency,
             payment_method,
-            orderid: item.connector_request_reference_id.clone(),
+            orderid: item.router_data.connector_request_reference_id.clone(),
         })
     }
 }
@@ -243,18 +276,17 @@ pub struct NmiCaptureRequest {
     pub amount: Option<f64>,
 }
 
-impl TryFrom<&types::PaymentsCaptureRouterData> for NmiCaptureRequest {
+impl TryFrom<&NmiRouterData<&types::PaymentsCaptureRouterData>> for NmiCaptureRequest {
     type Error = Error;
-    fn try_from(item: &types::PaymentsCaptureRouterData) -> Result<Self, Self::Error> {
-        let auth = NmiAuthType::try_from(&item.connector_auth_type)?;
+    fn try_from(
+        item: &NmiRouterData<&types::PaymentsCaptureRouterData>,
+    ) -> Result<Self, Self::Error> {
+        let auth = NmiAuthType::try_from(&item.router_data.connector_auth_type)?;
         Ok(Self {
             transaction_type: TransactionType::Capture,
             security_key: auth.api_key,
-            transactionid: item.request.connector_transaction_id.clone(),
-            amount: Some(utils::to_currency_base_unit_asf64(
-                item.request.amount_to_capture,
-                item.request.currency,
-            )?),
+            transactionid: item.router_data.request.connector_transaction_id.clone(),
+            amount: Some(item.amount),
         })
     }
 }
@@ -577,18 +609,15 @@ pub struct NmiRefundRequest {
     amount: f64,
 }
 
-impl<F> TryFrom<&types::RefundsRouterData<F>> for NmiRefundRequest {
+impl<F> TryFrom<&NmiRouterData<&types::RefundsRouterData<F>>> for NmiRefundRequest {
     type Error = Error;
-    fn try_from(item: &types::RefundsRouterData<F>) -> Result<Self, Self::Error> {
-        let auth_type: NmiAuthType = (&item.connector_auth_type).try_into()?;
+    fn try_from(item: &NmiRouterData<&types::RefundsRouterData<F>>) -> Result<Self, Self::Error> {
+        let auth_type: NmiAuthType = (&item.router_data.connector_auth_type).try_into()?;
         Ok(Self {
             transaction_type: TransactionType::Refund,
             security_key: auth_type.api_key,
-            transactionid: item.request.connector_transaction_id.clone(),
-            amount: utils::to_currency_base_unit_asf64(
-                item.request.refund_amount,
-                item.request.currency,
-            )?,
+            transactionid: item.router_data.request.connector_transaction_id.clone(),
+            amount: item.amount,
         })
     }
 }

## Type of Change
<!-- Put an `x` in the boxes that apply -->

- [ ] Bugfix
- [x] New feature
- [ ] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
- Addressing Issue: #2236 
- Modified two files in `hyperswitch/crates/router/src/connector/`
  - `nmi.rs`
    - Implement `get_currency_unit` function
    - Modify `ConnectorIntegration` implementations for `Nmi`
  - `nmi/transformers.rs`
    - Implement `NmiRouterData<T>` structure and functionality
    - Modify implementation for `NmiPaymentsRequest`


### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables

<!--
Provide links to the files with corresponding changes.

Following are the paths where you can find config files:
1. `config`
2. `crates/router/src/configs`
3. `loadtest/config`
-->


## Motivation and Context
<!--
Why is this change required? What problem does it solve?
If it fixes an open issue, please link to the issue here.

If you don't have an issue, we'd recommend starting with one first so the PR
can focus on the implementation (unless it is an obvious bug or documentation fix
that will have little conversation).
-->


## How did you test it?
<!--
Did you write an integration/unit/API test to verify the code changes?
Or did you test this change manually (provide relevant screenshots)?
-->
We need to create a payment using NMI and test the currency unit from connector response and connector dashboard.

## Checklist
<!-- Put an `x` in the boxes that apply -->

- [x] I formatted the code `cargo +nightly fmt --all`
- [ ] I addressed lints thrown by `cargo clippy`
- [ ] I reviewed the submitted code
- [ ] I added unit tests for my changes where possible
- [ ] I added a [CHANGELOG](/CHANGELOG.md) entry if applicable
