Behavior: Generates signed cookies required for secure streaming of a related asset (e.g., proxy video, preview). The response includes cookies both in the response headers (for browser-based playback) and in the response body (for programmatic access).

Authorization: Requires a valid Bearer token.

Side Effects: Signed streaming cookies are set in the HTTP response headers.

Error Scenarios: Returns 401 if the caller is not authenticated. Returns 404 if the asset or related asset is not found.