fix(users): add bad request for openidconnect

[racnan]

Type of Change

• [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.

Additional Changes

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

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.

How did you test it?

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.

Checklist

• [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

[semanticdiff-com[bot]]

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Changed Files

File	Status
crates/router/src/services/openidconnect.rs	33% smaller