Bug: fix(users): Add Bad request response in openidconnect



Currently, when users provide an invalid or expired code during SSO login, the system returns a 500 response. This is misleading, as the issue is with the client input rather than a server error. This change introduces a proper 400 BadRequest response to better reflect the actual problem and improve error handling.
diff --git a/crates/router/src/services/openidconnect.rs b/crates/router/src/services/openidconnect.rs
index ca20b021a56..69b890d657e 100644
--- a/crates/router/src/services/openidconnect.rs
+++ b/crates/router/src/services/openidconnect.rs
@@ -76,7 +76,14 @@ pub async fn get_user_email_from_oidc_provider(
         .exchange_code(oidc::AuthorizationCode::new(authorization_code.expose()))
         .request_async(|req| get_oidc_reqwest_client(state, req))
         .await
-        .change_context(UserErrors::InternalServerError)
+        .map_err(|e| match e {
+            oidc::RequestTokenError::ServerResponse(resp)
+                if resp.error() == &oidc_core::CoreErrorResponseType::InvalidGrant =>
+            {
+                UserErrors::SSOFailed
+            }
+            _ => UserErrors::InternalServerError,
+        })
         .attach_printable("Failed to exchange code and fetch oidc token")?;
 
     // Fetch id token from response

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

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

## Description
Added a BadRequest response for SSO login when an invalid authorization code is provided.
<!-- Describe your changes in detail -->


### Additional Changes

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

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2. `crates/router/src/configs`
3. `loadtest/config`
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## Motivation and Context
Currently, when users provide an invalid or expired code during SSO login, the system returns a 500 response. This is misleading, as the issue is with the client input rather than a server error. This change introduces a proper 400 BadRequest response to better reflect the actual problem and improve error handling.
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## How did you test it?
```sh
curl --location '<BASE URL>/user/oidc' \
--header 'Content-Type: application/json' \
--data '{
    "state": "<correct state>",
    "code": "<wrong code>"
}'
```
This should give `400` instead of 500.

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Or did you test this change manually (provide relevant screenshots)?
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## 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
