A simple favourite system that adds an artist to your favourites when
you go to their artist page for the first time.
Also, if you fetch something from an artist, they get automatically
added to the favourites.
This is pretty much just done by adding more crap to the main SQL
query, and has the disadvantage that the `artist_has_been_snatched`
CTE slows down the query a lot for the favourite filter (by 50% or
even sometimes 150% in a weird degenerate case). I think we can
optimize this somewhat, but that needs a small rewrite of the query
CTE stages.
Change-Id: I7aa6d99dc26e24eb22ef56ffd4d2db5c6978ad48
Reviewed-on: https://cl.tvl.fyi/c/depot/+/13238
Reviewed-by: Profpatsch <mail@profpatsch.de>
Tested-by: BuildkiteCI
bc09c01dfd
