Currently almost all mail tests run on mail.channel model. Indeed it is
the only model inheriting from mail.thread and mail.alias when having only
mail installed. However channel model have several specific features and
is not totally a standard mail.thread model. For example notification
recipients are computed a bit differently.
Since 4f9105a4ef mail module has a test
model allowing to perform tests on a very simple mail.thread-like model.
This commit make mail tests use this test model instead of mail.channel
everywhere it is possible. Channel model should be used only when tests
are channel-dependent.
If the 'To' of an incoming email is an alias on another model we now consider
this emails as a forward to a new alias. A use case for this is an email on
a task that should be considered as an issue and forwarded to another alias.
Thibault Delavallée