Error Handling: gracefully handle missing livekit service url in config

[BillCarsonFr]

Fixes #2971

How to test:

• Update the local config.json in public/ folder and remove the livekit entry

Will generate this screen:

I tried to put a clear and not technical message, with a call to action to contact the server admin.
The error code should be enough for the admin to know what to do

I tried to do a more complete test that would setup a lobby with a video preview and trigger this error, but I would need more time to do so. Any direction could help.

Update

Following internal discussions did a quick refactoring to improve error structure (add a category to match this document), and also added more details on the RTC focus error: Include the domain and better title/description.

See this commit: 2ba803f

Now Error is:

[hughns]

One material thing to look at:

• wording for ConnectionLostError

Otherwise just nits.

[hughns]

This is looking good to me 👍

As we are using existing strings for the "connection lost" description I think leave the wording as is.