A merge of upstream/master, resolving the conflicts created by that PR, and
f5bfe7a - re-enabling Google auth on top of those improvements (which made it more straightforward). Note, I also submitted this as a PR upstream (https://github.com/mozilla/pontoon/pull/1491), so if they accept it, we can re-converge
https://github.com/mozilla/pontoon/pull/1442 improved some of the auth code that we'd forked to allow for google auth, so this PR includes:
upstream/master, resolving the conflicts created by that PR, and