Add Discogs as source for Back Covers

[steveoat]

Thanks for providing access to back covers of albums. I know discogs also has some. Any chance you can use them as a source?

[paultaylor]

Currently we use a proxy to retrieve images from Discogs, and this only supports front images

We do plan to use Discogs back cover and also artist images, but not insignificant amount of work as will have to be done different to front images https://jthink.atlassian.net/browse/SONGKONG-2322