This is a preparatory commit for using isort for sorting all of our
imports, merging changes to files where we can easily review the
changes as something we're happy with.
These are also files with relatively little active development, which
means we don't expect much merge conflict risk from these changes.
Previously, we set restrict_to_domain and invite_required differently
depending on whether we were setting up a community or a corporate
realm. Setting restrict_to_domain requires validation on the domain of the
user's email, which is messy in the web realm creation flow, since we
validate the user's email before knowing whether the user intends to set up
a corporate or community realm. The simplest solution is to have the realm
creation flow impose as few restrictions as possible (community defaults),
and then worry about restrict_to_domain etc. after the user is already in.
We set the test suite to explictly use the old defaults, since several of
the tests depend on the old defaults.
This commit adds a database migration.