Updates coder/customers#365
This PR updates our migration framework to run all migrations in a single transaction. This is the same behavior we had in v1 and ensures that failed migrations don't bring the whole deployment down. If a migration fails now, it will automatically be rolled back to the previous version, allowing the deployment to continue functioning.
* chore: rename `git_auth` to `external_auth` in our schema
We're changing Git auth to be external auth. It will support
any OAuth2 or OIDC provider.
To split up the larger change I want to contribute the schema
changes first, and I'll add the feature itself in another PR.
* Fix names
* Fix outdated view
* Rename some additional places
* Fix sort order
* Fix template versions auth route
* Fix types
* Fix dbauthz
