A key part of this is the new helper, get_user_by_delivery_email. Its
verbose name is important for clarity; it should help avoid blind
copy-pasting of get_user (which we'll also want to rename).
Unfortunately, it requires detailed understanding of the context to
figure out which one to use; each is used in about half of call sites.
Another important note is that this PR doesn't migrate get_user calls
in the tests except where not doing so would cause the tests to fail.
This probably deserves a follow-up refactor to avoid bugs here.
Importing the Django test client is somewhat expensive, and we only
use it within one view function that's not used in production. So
there's a significant startup-time performance optimization in doing
an import inside the view code.
This often can cause minor caching problems.
Obviously, it'd be better if we had access to the AST and thus could
do this rule for UserProfile objects in general.
Seems like the more logical check. Also, the previous code makes it feel
like there is a potential vulnerability where one could get an email change
object in a realm where email changes are disabled, and then open that link
while logged in to a different realm.
While we're at it, remove the unnecessary check that the user is
logged in when clicking the confirmation link; that creates
unnecessary trouble for users who use multiple browsers.