This change is mostly based on a similar commit from hackerkid
in a feature branch. It borrows both code and ideas. Some of
it's my own stuff, as I was working on a newer branch.
We now call get_user_including_cross_realm_email() inside of
user_profiles_from_unvalidated_emails(), instead of using
get_user_profile_by_email.
This requires a few of our callers to pass down sender into us.
One consequence of this change is that we change the symptoms
for trying to send to emails outside of your realm. In some
cases, we simply raise an error that an email is invalid to us
instead of getting into the deeper validate_recipient_user_profiles
check.
We are trying to convert emails to user_profiles earlier in
the codepath. This may cause subtle changes in which errors
appear, but it's probably generally good to report on bad
addressees sooner than later.
This class simplifies the calling sequence to methods like
check_message and _internal_prep_message, and it's also more
type safe.
Checking for message types is encapsulated with calls to is_stream()
and is_private(). There are also shortcut constructors when you
know that the type of the address (stream vs. private), which is often.