Unique RTMP-URL for self-streams

[carlobortolan]

Is your feature request related to a problem? Please describe.

• Having to copy and paste a new URL every time a lecturer wants to start a stream can become annoying.
• Managing multiple URLs for each course is inconvenient for lecturers who teach different courses.

Describe the solution you'd like
Having one URL that doesn't change for every stream, with a token that a lecturer can create once and then use for all lectures: A lecturer could create a "lecturer token" in the token panel of the admin dashboard. Then, an RTMP-Proxy could exchange this token with the stream-specific URL to redirect an incoming self-stream request to the correct ingest server.

Describe alternatives you've considered
Keep the current system.

Additional context
For the RTMP-Proxy: https://github.com/arut/nginx-rtmp-module
(@SebiWrn)