Log Message:
Update gst-rtsp-server to 1.12.3

## GStreamer RTSP server

- The RTSP server now also supports Digest authentication in addition to Basic
  authentication.
- The `GstRTSPClient` class has gained a `pre-*-request` signal and virtual
  method for each client request type, emitted in the beginning of each rtsp
  request. These signals or virtual methods let the application validate the
  requests, configure the media/stream in a certain way and also generate error
  status codes in case of an error or a bad request.