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.
PIG208
Anders Kaseorg
Mohit Gupta