Webhook scrobbler

[kgarner7]

This PR adds the ability to send scrobbles to one or more arbitrary endpoints. It's really only useful for people who want to display their now playing status. The expected interface is inspired by Listenbrainz. I'd be very open to discussing a better API spec (it shouldn't be hard to do).

Isn't this basically ListenBrainz, but for multiple endpoints? Pretty much.

Error response
On an error, the endpoint MUST respond with JSON with the following properties:

• error: int, a non-zero value
• message: the specific error message

Mandatory parameters:

• token: the specific user token
• apiKey: an api key for the server

/validate
A webhook MUST have an endpoint BASE_URL/validate that accepts POST requests with JSON body with the mandatory parameters

On a success the server MUST respond with JSON with one key:

• userName: the respective user name

/scrobble
A webhook MUST have an endpoint BASE_URL/scrobble that accepts a POST request with JSON with mandatory parameters, as well as:

• album: string, the track album. Can be empty string
• albumArtist: string, the album artist. Can be empty
• artist: string, the track artist
• duration: int, length of the track in seconds. required
• mbid: musicbrainz track id. can be empty
• track: the track title. required
• trackNumber: the number of the track. Can be zero.

On a success, the server MUST respond with an empty JSON object.

[github-actions]

Download the artifacts for this pull request:

• binaries.zip
• js-bundle.zip

[Skarlett]

This would be really nice with last.fm too

[github-actions]

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