NotSupportedError when specifying a user by email to Django commands using UserArgument

Found while working on #1421 (closed): The arkindex.project.argparse.UserArgument tries to use email__icontains, which uses a LIKE operator, but PostgreSQL does not like this on our case-insensitive email field:

λ ./manage.py clone_process --creator lol@lol.lol
# or, with #1421:
λ ./manage.py fake_worker_run --user lol@lol.lol
...
NotSupportedError: nondeterministic collations are not supported for LIKE