Bug: [FEATURE]: [Nexi Nets] 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/nexinets.rs b/crates/router/src/connector/nexinets.rs
index 30ae4ab25e5..ac0d7494d2d 100644
--- a/crates/router/src/connector/nexinets.rs
+++ b/crates/router/src/connector/nexinets.rs
@@ -76,6 +76,10 @@ impl ConnectorCommon for Nexinets {
         "nexinets"
     }
 
+    fn get_currency_unit(&self) -> api::CurrencyUnit {
+        api::CurrencyUnit::Minor
+    }
+
     fn common_get_content_type(&self) -> &'static str {
         "application/json"
     }
@@ -200,9 +204,15 @@ impl ConnectorIntegration<api::Authorize, types::PaymentsAuthorizeData, types::P
         &self,
         req: &types::PaymentsAuthorizeRouterData,
     ) -> CustomResult<Option<types::RequestBody>, errors::ConnectorError> {
-        let req_obj = nexinets::NexinetsPaymentsRequest::try_from(req)?;
+        let connector_router_data = nexinets::NexinetsRouterData::try_from((
+            &self.get_currency_unit(),
+            req.request.currency,
+            req.request.amount,
+            req,
+        ))?;
+        let connector_req = nexinets::NexinetsPaymentsRequest::try_from(&connector_router_data)?;
         let nexinets_req = types::RequestBody::log_and_get_request_body(
-            &req_obj,
+            &connector_req,
             utils::Encode::<nexinets::NexinetsPaymentsRequest>::encode_to_string_of_json,
         )
         .change_context(errors::ConnectorError::RequestEncodingFailed)?;
diff --git a/crates/router/src/connector/nexinets/transformers.rs b/crates/router/src/connector/nexinets/transformers.rs
index 2af3ee0a1bb..ce34fe8f5a2 100644
--- a/crates/router/src/connector/nexinets/transformers.rs
+++ b/crates/router/src/connector/nexinets/transformers.rs
@@ -14,7 +14,10 @@ use crate::{
     consts,
     core::errors,
     services,
-    types::{self, api, storage::enums, transformers::ForeignFrom},
+    types::{
+        self, api, storage::enums, transformers::ForeignFrom, PaymentsAuthorizeData,
+        PaymentsResponseData,
+    },
 };
 
 #[derive(Debug, Serialize)]
@@ -27,7 +30,6 @@ pub struct NexinetsPaymentsRequest {
     payment: Option<NexinetsPaymentDetails>,
     #[serde(rename = "async")]
     nexinets_async: NexinetsAsyncDetails,
-    merchant_order_id: Option<String>,
 }
 
 #[derive(Debug, Serialize, Default)]
@@ -163,29 +165,70 @@ pub struct ApplepayPaymentMethod {
     token_type: String,
 }
 
-impl TryFrom<&types::PaymentsAuthorizeRouterData> for NexinetsPaymentsRequest {
+#[derive(Debug, Serialize)]
+pub struct NexinetsRouterData<T> {
+    amount: i64,
+    router_data: T,
+}
+impl<T>
+    TryFrom<(
+        &types::api::CurrencyUnit,
+        types::storage::enums::Currency,
+        i64,
+        T,
+    )> for NexinetsRouterData<T>
+{
     type Error = error_stack::Report<errors::ConnectorError>;
-    fn try_from(item: &types::PaymentsAuthorizeRouterData) -> Result<Self, Self::Error> {
-        let return_url = item.request.router_return_url.clone();
+    fn try_from(
+        (_currency_unit, _currency, amount, item): (
+            &types::api::CurrencyUnit,
+            types::storage::enums::Currency,
+            i64,
+            T,
+        ),
+    ) -> Result<Self, Self::Error> {
+        Ok(Self {
+            amount,
+            router_data: item,
+        })
+    }
+}
+
+impl
+    TryFrom<
+        &NexinetsRouterData<
+            &types::RouterData<
+                types::api::payments::Authorize,
+                PaymentsAuthorizeData,
+                PaymentsResponseData,
+            >,
+        >,
+    > for NexinetsPaymentsRequest
+{
+    type Error = error_stack::Report<errors::ConnectorError>;
+    fn try_from(
+        item: &NexinetsRouterData<
+            &types::RouterData<
+                types::api::payments::Authorize,
+                PaymentsAuthorizeData,
+                PaymentsResponseData,
+            >,
+        >,
+    ) -> Result<Self, Self::Error> {
+        let return_url = item.router_data.request.router_return_url.clone();
         let nexinets_async = NexinetsAsyncDetails {
             success_url: return_url.clone(),
             cancel_url: return_url.clone(),
             failure_url: return_url,
         };
-        let (payment, product) = get_payment_details_and_product(item)?;
-        let merchant_order_id = match item.payment_method {
-            // Merchant order id is sent only in case of card payment
-            enums::PaymentMethod::Card => Some(item.connector_request_reference_id.clone()),
-            _ => None,
-        };
+        let (payment, product) = get_payment_details_and_product(&item.router_data)?;
         Ok(Self {
-            initial_amount: item.request.amount,
-            currency: item.request.currency,
+            initial_amount: item.router_data.request.amount,
+            currency: item.router_data.request.currency,
             channel: NexinetsChannel::Ecom,
             product,
             payment,
             nexinets_async,
-            merchant_order_id,
         })
     }
 }
@@ -312,23 +355,12 @@ pub struct NexinetsPaymentsMetadata {
 }
 
 impl<F, T>
-    TryFrom<
-        types::ResponseRouterData<
-            F,
-            NexinetsPreAuthOrDebitResponse,
-            T,
-            types::PaymentsResponseData,
-        >,
-    > for types::RouterData<F, T, types::PaymentsResponseData>
+    TryFrom<types::ResponseRouterData<F, NexinetsPreAuthOrDebitResponse, T, PaymentsResponseData>>
+    for types::RouterData<F, T, PaymentsResponseData>
 {
     type Error = error_stack::Report<errors::ConnectorError>;
     fn try_from(
-        item: types::ResponseRouterData<
-            F,
-            NexinetsPreAuthOrDebitResponse,
-            T,
-            types::PaymentsResponseData,
-        >,
+        item: types::ResponseRouterData<F, NexinetsPreAuthOrDebitResponse, T, PaymentsResponseData>,
     ) -> Result<Self, Self::Error> {
         let transaction = match item.response.transactions.first() {
             Some(order) => order,
@@ -421,13 +453,12 @@ pub struct NexinetsPaymentResponse {
     pub transaction_type: NexinetsTransactionType,
 }
 
-impl<F, T>
-    TryFrom<types::ResponseRouterData<F, NexinetsPaymentResponse, T, types::PaymentsResponseData>>
-    for types::RouterData<F, T, types::PaymentsResponseData>
+impl<F, T> TryFrom<types::ResponseRouterData<F, NexinetsPaymentResponse, T, PaymentsResponseData>>
+    for types::RouterData<F, T, PaymentsResponseData>
 {
     type Error = error_stack::Report<errors::ConnectorError>;
     fn try_from(
-        item: types::ResponseRouterData<F, NexinetsPaymentResponse, T, types::PaymentsResponseData>,
+        item: types::ResponseRouterData<F, NexinetsPaymentResponse, T, PaymentsResponseData>,
     ) -> Result<Self, Self::Error> {
         let transaction_id = Some(item.response.transaction_id.clone());
         let connector_metadata = serde_json::to_value(NexinetsPaymentsMetadata {

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

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

## Description
This pull request implements the get_currency_unit from the ConnectorCommon trait for the Nexinets connector. This function allows connectors to declare their accepted currency unit as either Base or Minor. For Nexinets it accepts currency as Minor units.


### Additional Changes

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


Following are the paths where you can find config files:
1. crates/router/src/connector/nexinets.rs
2. crates/router/src/connector/nexinets/transformers.rs




## Motivation and Context


Closes #2233 



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