Use registry get_defaults() to return built-in hosting services.

Review Request #12209 — Created March 24, 2022 and submitted — Latest diff uploaded


Review Board


Entry points are fantastic, and they're a great way for us to allow
third parties to integrate their own plugins with Review Board.
Unfortunately, if there's a VersionConflict present in the install, no
entry points will load, even if things will otherwise work. The result
of this is that none of our built-in services will work properly.

This change moves our built-ins directly into the registry's
get_defaults() method, rather than using entry points. Any third-party
services will still be loaded from entry points afterwards.

Started with a fresh database and virtualenv. Saw that built-in services
were available in the "Add Repository" form.