A couple of weird caveats:
* If we can't validate your macaroon, we fall back to checking that
your access token is in the DB, and ignoring the failure
* Even if we can validate your macaroon, we still have to hit the DB to
get the access token ID, which we pretend is a device ID all over the
codebase.
This mostly adds the interesting code, and points out the two pieces we
need to delete (and necessary conditions) in order to fix the above
caveats.
Removes device_id and ClientInfo
device_id is never actually written, and the matrix.org DB has no
non-null entries for it. Right now, it's just cluttering up code.
This doesn't remove the columns from the database, because that's
fiddly.
V2 Registration forced everyone (including ASes) to create a password for a
user, when ASes should be able to omit passwords. Also unbreak AS registration
in general which checked too early if the given username was claimed by an AS;
it was checked before knowing if the AS was the one doing the registration! Add
unit tests for AS reg, user reg and disabled_registration flag.
Add logic to map the appservice token to the autogenned appservice user ID.
Add unit tests for all forms of get_user_by_req (user/appservice,
valid/bad/missing tokens)
