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.
This commit creates a new organization setting that determines whether
a user can invite other users to streams. Previously this was linked
to the waiting period threshold, but this was both not documented and
overly limiting.
With significant tweaks by tabbott to change the database model to not
involve two threshhold fields, edit the tests, etc.
This requires follow-up work to make the create stream policy setting
work how this code implies it should.
Fixes#12042.
Tim Abbott
David Wood