* [bugfix] player: use userId, other fixes
This PR primarily resolves#1928 by switching the foreign key of `player` from `user.user_name` to `user.id`.
There are also a few other fixes/changes:
- For some bizarre reason, `ip_address` is never returned from `read`/`get`. Change the field to `ip`, which works. Somehow
- Update `players_test.go` mock to also check for user agent, replicating the actual code
- Update `player_repository.go` `isPermitted` to check user id. I don't know how this worked before...
- tests!
- a few places referred to `typ`, when it is really `userAgent`. Change the field names
* baseRequest -> selectPlayer
* remove comment
* update migration, make all of persistence foreign key enabled
* maybe don't forget to save the file first
* Refactor session_keys to its own package
* Adjust play_tracker
- Don't send external NowPlaying/Scrobble for tracks with unknown artist
- Continue to the next agent on error
* Implement ListenBrainz Agent and Auth Router
* Implement frontend for ListenBrainz linking
* Update listenBrainzRequest
- Don't marshal Player to json
- Rename Track to Title
* Return ErrRetryLater on ListenBrainz server errors
* Add tests for listenBrainzAgent
* Add tests for ListenBrainz Client
* Adjust ListenBrainzTokenDialog to handle errors better
* Refactor listenbrainz.formatListen and listenBrainzRequest structs
* Refactor agent auth_routers
* Refactor session_keys to agents package
* Add test for listenBrainzResponse
* Add tests for ListenBrainz auth_router
* Update ListenBrainzTokenDialog and auth_router
* Adjust player scrobble toggle
