Add flexible application status endpoint

[github4touchdouble]

Currently, only the following endpoints exist for modifying the application.status field:

• PATCH /accept
• PATCH /reject

These endpoints are tailored to specific status changes, limiting extensibility and the ability to reset application.status to null. To ensure future scalability for additional application states and to allow resetting the status, we propose introducing for example:

• A generalized PATCH endpoint (e.g., PATCH /status)
• A dedicated PATCH /reset endpoint for resetting application.status to null.