First iteration. The configuration interface will change.
Run the container with the GST_PIPELINE_STRING environment variable
set to define the GStreamer pipeline and the RTSP server location:
GST_PIPELINE_STRING=videotestsrc ! video/x-raw,width=1920,height=1080,format=I420,framerate=15/1 ! clockoverlay ! x264enc speed-preset=ultrafast bitrate=2000 ! video/x-h264,profile=baseline ! rtspclientsink protocols=tcp location=rtsp://host.docker.internal:8554/videotest