Thumbnail redirect

[pbinkley]

• Analysis of the Apache logs for Hydranorth showed one more pattern that we should redirect (in addition to all the other work in #460): /files/:noid/:filename?file=thumbnail (e.g. /files/c0r967375k/Nosworthy-FINAL-Jan%206%202016.pdf?file=thumbnail). "thumbnail" is the only value for "file" that we need to handle. If the file designated by :filename exists, we should return a permanent redirect to the thumbnail for that file. If the file doesn't exist, we should return 410 Gone.

• and the logs show that the two #no_longer_supported redirects are now unnecessary, getting negligible hits and not related to print citations. They can be removed.

get '/public/view/author/:username', to: 'redirect#no_longer_supported'
get '/action/submit/init/thesis/:uuid', to: 'redirect#no_longer_supported'

[cwant]

Just a note before I forget the conversation (slack) from yesterday: with the thumbnail server going into production, a question is which thumbnail do we redirect them to? Will thumbnails have permanent links, or will their links bounce around between servers?

Another note, the second bullet point was addressed in PR #460

[pbinkley]

The final target url pattern for thumbnails won't be in place until #435 is done, so it isn't worth working on this at this point, I think. Until then thumbnails will have a session-dependent url; after then they'll have a fixed url.