Auto connect on new streamer

[mcottontensor]

Relevant components:

• Signalling server
• Frontend library
• Frontend UI library
• Matchmaker
• Platform scripts
• SFU

Problem statement:

If the front end tries to join a stream before the streamer is connected it requires a click to connect once the streamer has connected.

Solution

This adds a new signalling message to the signalling server that broadcasts to all players that a new streamer has connected to the signalling server. The front end will respond to this if it's waiting, by auto joining the new stream.

Test Plan and Compatibility

None

[lukehb]

Hmmm, I would really prefer us to not add a new protocol message until we have a mechanism to transmit the signaling protocol and version.

If we absolutely can't achieve this another way then I guess by our own rules:

https://github.com/EpicGames/PixelStreamingInfrastructure/blob/master/SignallingWebServer/Docs/SignallingProtocol.md

This qualifies as a minor version bump in the signalling protocol (as it is independent and not a required message).

Could we also just sit in a timer and try again every few seconds if we couldn't connect and got back no streamers connected. I know it is more wasteful - but also no signaling change.

What do you think @mcottontensor?

[mcottontensor]

Fair. I can update it to just be a timer.

Rewrote the implementation.

[lukehb]

Tiny change to expose interval as a setting.

[lukehb]

Approved with suggestion to change most recent setting name.