Instead of using request.POST to get any potential `sender`
parameters for `send_message_backend`, moves it to the REQ
framework parameters as `req_sender`.
Also, updates `create_mirrored_message_users` to take specific
parameters instead of an HTTP request parameter, which then
accessed parameters via request.POST. And updates existing tests
for those changes.
This migrates some mocked Request class and mocked request achieved
with namedtuple in test_decorators and test_mirror_users to use the
refactored HostMockRequest.
Since weakref cannot be used with namedtuple, this old way of mocking a
request object should be migrated to using HostRequestMock. Only after
this change we can extract client from the request object and store it
via ZulipRequestNotes.
The commit moves, test_create_mirror_user_despite_race which is not related
to message sending from MessagePOSTTest class in test_message_send.py to
test_mirror_users.py.
Starting with extracting out MirroredMessageUsersTests as it is related to
mirror users than anything message-specific.
In a future commit, may extract out some tests from MessagePOSTTest as well
but still deciding on those.