Add video calls

[nicksellen]

Backend PR (initial work) https://github.com/karrot-dev/karrot-backend/pull/1283 merged Backend PR (adding webhooks) https://github.com/karrot-dev/karrot-backend/pull/1284 Branch deployment: https://add-video-calls.dev.karrot.world

What does this PR do?

My christmas "fun" project 🥳 🎄

Uses https://livekit.io/ behind the scenes (and I set up a self-hosted server to use at https://livekit.karrot.world/).

• feature is called "meet"
• must be enabled on a per-group basis
• then gives you "meet buttons" in various places:
  • top of group wall
  • inside place header
  • on joined activity
  • activity chat header
  • user chat header
• full screen mode only

Future things it could have, but not right now:

• keep track of the rooms inside karrot db using livekit webhooks, which would enable:
  • show how many people in a room on the button
  • have other indicators to show a call is happening, e.g. in side menu
• external call links so anyone can join even if not on karrot
• screensharing
• meeting chat (reuse existing chat if relevant? e.g. activity/user calls?)
• meeting notes? pad?
• mini view, so you can keep navigating around the site
• make it optional whether an activity has it enabled?
• end 2 end encryption (there is some facility for this with livekit)
• I'm sure plenty of UI improvements, I haven't tried it with many people....

Desktop:

Mobile:

Links to related issues

Checklist

• [ ] added a test, or explain why one is not needed/possible...
• [ ] no unrelated changes
• [ ] asked someone for a code review
• [ ] joined #karrot:matrix.org
• [ ] added an entry to CHANGELOG.md (description, pull request link, username(s))
• [ ] tried out on a mobile device (does everything work as expected on a smaller screen?)

[codecov[bot]]

Codecov Report

Attention: 569 lines in your changes are missing coverage. Please review.

Comparison is base (fc4c7b9) 74.40% compared to head (2a547a3) 73.90%. Report is 1 commits behind head on master.

Files	Patch %	Lines
src/meet/helpers.js	16.51%	450 Missing :warning:
src/meet/components/SelectDevices.vue	0.00%	65 Missing :warning:
src/meet/components/MeetButton.vue	82.88%	19 Missing :warning:
src/utils/queryHelpers.js	21.42%	11 Missing :warning:
src/App.vue	30.00%	7 Missing :warning:
src/users/helpers.js	50.00%	5 Missing :warning:
src/authuser/helpers.js	57.14%	3 Missing :warning:
src/base/helpers.js	75.00%	3 Missing :warning:
src/meet/queries.js	93.54%	2 Missing :warning:
src/utils/utils.js	50.00%	2 Missing :warning:
... and 2 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2699 +/- ## ========================================== - Coverage 74.40% 73.90% -0.51% ========================================== Files 392 404 +12 Lines 42704 44084 +1380 Branches 2434 2453 +19 ========================================== + Hits 31775 32579 +804 - Misses 10929 11505 +576 ```

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