**feat**: create `SendGrantValidator` and initial `SendPasswordValidator` for Send access grants
**feat**: add feature flag to toggle Send grant validation logic
**feat**: add Send client to Identity and update `ApiClient` to generic `Client`
**feat**: register Send services in DI pipeline
**feat**: add claims management support to `ProfileService`
**feat**: distinguish between invalid grant and invalid request in `SendAccessGrantValidator`
**fix**: update parsing of `send_id` from request
**fix**: add early return when feature flag is disabled
**fix**: rename and organize Send access scope and grant type
**fix**: dotnet format
**test**: add unit and integration tests for `SendGrantValidator`
**test**: update OpenID configuration and API resource claims
**doc**: move documentation to interfaces and update inline comments
**chore**: add TODO for future support of `CustomGrantTypes`
