Merge auth-server and oauth-server 🛠

[vladikoff]

It was a long time proposal from @rfk to uplift the oauth-server into this repo. With the recent exploration into improving devices API I think we finally got to the point where it is worth doing this to make it easier to develop new OAuth features. Let me know if you are against this idea in the comments below. Otherwise Like and Subscribe.

I began work on syncing up dependencies in:

mozilla/fxa-oauth-server#615
mozilla/fxa-oauth-server#616

[philbooth]

Woop! Can we merge fxa-auth-db-mysql in too?!

[rfk]

@rfk to merge with other bug about this

[rfk]

I accidentally created a dupe of this over in #2679, but this one has emoji so I'm going to close out #2679 and migrate its checklist over to here.

[rfk]

Actually no, this issue is different and broader than #2679; this issue is talking about actually merging the two servers together, while #2679 is a pre-req about making them a monorepo. Let's push forward on the work in #2679 first and we can pick up this one again when @vladikoff returns.

[vladikoff]

Remaining work is in #2748