This is an album cover HTTP service.
To get an album cover image, send an HTTP request to
/covers?artist=$artist&album=$album
If the cover is found, a 200 OK is returned along with the cover file. If the cover cannot be found, a 404 NOT FOUND is returned. If the request is erroneous, a 400 BAD REQUEST is returned.
DiscoGs is used as the cover backend. Covers are cached on the local filesystem in a directory specified by system
property cover.dir. DiscoGs requires OAuth authentication, so you need to specify OAuth credentials in a file
specified by system property discogs.oauth.