POST and DELETE operations in /users/me/alert_words may leave the
user's list of alert words in an unknown state: POSTing adds words to a
list that the client may not know from the begining, and the same with
DELETE.
Replying with the current status of the alert words list is the best way
of letting the client alter the list and knowing its contents after
being updated with a single query.
This is especially useful taking into account that POSTing words that
were already present and DELETing non-existing words both produce a
successful response.
An extra test has been added to avoid leaving GET /users/me/alert_words
too untested.
This fixes most cases where we were assigning a user to
the var email and then calling get_user_profile_by_email with
that var.
(This was fixed mostly with a script.)
The example_user() function is specifically designed for
AARON, hamlet, cordelia, and friends, and it allows a concise
way of using their built-in user profiles. Eventually, the
widespread use of example_user() should help us with refactorings
such as moving the tests users out of the "zulip.com" realm
and deprecating get_user_profile_by_email.
