These functions don't really belong in actions.py, so we move them out,
into email_mirror_helpers.py. They can't go directly into
email_mirror.py or we'd get circular imports resulting in ImportError.
We change the send_to_email_mirror management command, to send messages
to the email mirror through the mirror_email_message function instead of
process_message - this makes the message follow a similar codepath as
emails sent into the mirror with the postfix configuration, which means
going through the MirrorWorker queue. The reason for this is to make
this command useful for testing the new email mirror rate limiter.
Closes#11195. We add a management command to allow us to send emails
to the email mirror directly. The command doesn't require any
configuring of email sending or receiving for the email mirror,
it passes the emails directly using the process_message function.
Mateusz Mandera
Anders Kaseorg