This fixes up some issues with the oauth2_provider upgrade.
First, we now set an explicit default value for Grant.claims, which is

needed on everything but MySQL and was missing in my previous change.
We also now manage the list of recorded migrations for oauth2_provider.

Post-upgrade, we do another clear of the list of recorded migrations and

then we populate it with the full list that ships with oauth2_provider

1.6.3. This avoids potential dependency issues with migrations, and it

avoids the Django system checks complaining about missing migrations

that still need to be applied.

Tested a new round of upgrades. Verified that Django's system checks

no longer saw missing migrations.