Verbatim credits (credits sourcing)

[towerofnix]

Intro/suggestion from Lanolin (#hsmusic-chat):

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I just want to point out the way I'm sourcing from releases on multiple platforms, doubling an entry from both Bandcamp and YouTube though they're similar (but not identical), and including the Bandcamp credits blurb as originally written.

I'm not going over the thousands of tracks already on the wiki present on Bandcamp right now, but I think it would be right to always archive credits text as commentary on principle.

We can implement these commentary entries as "collapsed by default" a little later, as we add them across more pages, since they're primarily reference material and usually just duplicate stuff that's in the normal UI places.

This would include reference lists precisely as written (with wiki links applied, of course). Although it's content and not represented as data, it would help preserve where artists list their track as referencing Black instead of Liquid Negrocity (and the wiki disagrees re: our own track referencing data), for example.

They should probably go on a separate field than Commentary, also.
It doesn't make sense to tally or include them in the commentary section on an artist page, nor generally to put them in an album's commentary page.

Also, this would mean we can collapse - and expand - the whole credits section (on a track page) rather than individual credits-y commentary entries.

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Our plan for this is to use almost exactly the same interface and design as Multiple Lyrics — these features are strongly related.

[towerofnix]

Must be implemented alongside hsmusic/bc-art#10, which means this is pending hsmusic/bc-art#7 and hsmusic/bc-art#8. See #hsmusic-chat for general dependency discussion.