Listenbrainz scrobbling (#1424)

* 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

ui/src/actions/dialogs.js

@@ -4,6 +4,8 @@ export const DUPLICATE_SONG_WARNING_OPEN = 'DUPLICATE_SONG_WARNING_OPEN'
 export const DUPLICATE_SONG_WARNING_CLOSE = 'DUPLICATE_SONG_WARNING_CLOSE'
 export const EXTENDED_INFO_OPEN = 'EXTENDED_INFO_OPEN'
 export const EXTENDED_INFO_CLOSE = 'EXTENDED_INFO_CLOSE'
+export const LISTENBRAINZ_TOKEN_OPEN = 'LISTENBRAINZ_TOKEN_OPEN'
+export const LISTENBRAINZ_TOKEN_CLOSE = 'LISTENBRAINZ_TOKEN_CLOSE'
 
 export const openAddToPlaylist = ({ selectedIds, onSuccess }) => ({
   type: ADD_TO_PLAYLIST_OPEN,
@@ -34,3 +36,11 @@ export const openExtendedInfoDialog = (record) => {
 export const closeExtendedInfoDialog = () => ({
   type: EXTENDED_INFO_CLOSE,
 })
+
+export const openListenBrainzTokenDialog = () => ({
+  type: LISTENBRAINZ_TOKEN_OPEN,
+})
+
+export const closeListenBrainzTokenDialog = () => ({
+  type: LISTENBRAINZ_TOKEN_CLOSE,
+})