Return song durations for shows when listing all shows for a specific song

[farktronix]

Relisten on iOS would like to display song durations for shows when listing all shows for a song (RelistenNet/relisten-ios#125)

When a client hits the /api/v2/artists/{artistIdOrSlug}/songs/{idAndSlug} endpoint, can the server pick the first source for that show and return the duration of the given song in the source? If there are multiple songs that match the song title then the longest duration should be returned.

[alecgorge]

The reason this is like this is because there isn't anything that actually links a specific "track" in a source to a "song" in a setlist. (song name doesn't work—think "Fire on the Mountain ->" or "Frie On the MOUNTAIN **>" or any variation on that—it shouldn't happen on phish.in but it still does)

phish.in is the only upstream source that provides a solid 1:1 between setlist songs and tracks. we'll probably need to special case this at every level (importer, queries, etc), then put it behind an artist feature flag for client handling/rendering

[farktronix]

It won't help with typos, but it seems like you could get 90% of the way there by doing a lowercase prefix search on the titles. If some of the shows don't match up it's fine to have them blank, and it'd be nice to be able to see (and eventually sort by) song duration in that view