Bug: [BUG] Adyen throws `500` when doing PSync call for non-redirection flow



### Bug Description

Adyen throws `500` when doing PSync call for non-redirection flow. 

### Expected Behavior

Since Adyen doesn't PSync for normal non-redirection flow, it should tell user that PSync is not supported instead of throwing `internal server error`

### Actual Behavior

Throws `500` in the response.

### Steps To Reproduce

Provide an unambiguous set of steps to reproduce this bug. Include code or configuration to reproduce, if relevant.
1. Make a payment through Adyen
2. Make a PSync call given that the `encoded_data` is `None`
3. Throws `500`


### Context For The Bug

Adyen for normal flow, gives the payment status in the form of Webhooks instead of a PSync response. So basically, PSync should not work when performed for non-redirection flows as PSync only gives the redirection URL here in Adyen (`encoded_data` contains the `redirectUrl`

### Environment

Are you using hyperswitch hosted version?  
Yes and No. Error occurs everywhere (Locally as well as on Integ and Sandbox)
x-request-id: `75a306af-cc07-41d5-a62c-4716659e9aac`

### Have you spent some time to check if this bug has been raised before?

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

### Have you read the Contributing Guidelines?

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

### Are you willing to submit a PR?

Yes I am willing to submit a PR!
diff --git a/crates/router/src/connector/adyen.rs b/crates/router/src/connector/adyen.rs
index 380a96c6b57..149beb97c65 100644
--- a/crates/router/src/connector/adyen.rs
+++ b/crates/router/src/connector/adyen.rs
@@ -310,12 +310,19 @@ impl
         &self,
         req: &types::RouterData<api::PSync, types::PaymentsSyncData, types::PaymentsResponseData>,
     ) -> CustomResult<Option<String>, errors::ConnectorError> {
+        // Adyen doesn't support PSync flow. We use PSync flow to fetch payment details,
+        // specifically the redirect URL that takes the user to their Payment page. In non-redirection flows,
+        // we rely on webhooks to obtain the payment status since there is no encoded data available.
+        // encoded_data only includes the redirect URL and is only relevant in redirection flows.
         let encoded_data = req
             .request
             .encoded_data
             .clone()
             .get_required_value("encoded_data")
-            .change_context(errors::ConnectorError::RequestEncodingFailed)?;
+            .change_context(errors::ConnectorError::FlowNotSupported {
+                flow: String::from("PSync"),
+                connector: self.id().to_string(),
+            })?;
 
         let adyen_redirection_type = serde_urlencoded::from_str::<
             transformers::AdyenRedirectRequestTypes,

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

- [x] Bugfix

## Description
<!-- Describe your changes in detail -->
This PR address Internal Server Error that arised when calling PSync in non-redirection flow.
`contains_encoded_data` in the else part is needed if not, status about the payments for bank redirects never change.

## 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 its an obvious bug or documentation fix
that will have little conversation).
-->
Doing a PSync call used to `500, Internal Server Error` as the `encoded_data` passed `None` value during non-redirection flow.


## 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)?
-->
Couldn't test by running `adyen.rs` as API keys contain symbols such as `)` and `]` that result in internal `toml` error. Tested manually as of now.
Manually.

Normal Flow:
<img width="1307" alt="image" src="https://github.com/juspay/hyperswitch/assets/69745008/e4a9af29-6872-498d-9bc4-bc1d24cc0058">

<img width="1307" alt="image" src="https://github.com/juspay/hyperswitch/assets/69745008/096812a0-7521-4c98-a7b4-9ec61c59e803">

Redirection Flow:
<img width="1301" alt="image" src="https://github.com/juspay/hyperswitch/assets/69745008/d43da29e-1f48-43ff-9564-1933ec9986cd">
<img width="1301" alt="image" src="https://github.com/juspay/hyperswitch/assets/69745008/7da08204-4267-48ae-86ce-efe6a6c36bdb">
<img width="1009" alt="image" src="https://github.com/juspay/hyperswitch/assets/69745008/06120a37-e014-40af-93e9-05dcdb0f938b">
<img width="1150" alt="image" src="https://github.com/juspay/hyperswitch/assets/69745008/2e8375b8-08e2-4670-a049-e2012920fd82">



## 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 submitted code
- [ ] I added unit tests for my changes where possible
- [ ] I added a [CHANGELOG](/CHANGELOG.md) entry if applicable
