Feature Request: make video sources configurable

[schuettloeffel-elsa]

In our setup we cant use multi streams, so it would be great if there was a setting to configure the available video sources so that we could disable the "Display & camera"-option.

Maybe something like this:

[upload]
available_video_sources = ["display", "display-camera", "camera"]

Then we could turn it to:

[upload]
available_video_sources = ["display", "camera"]