[MERGE] mail: improve alias security and alias check on channel model

This commit links the alias security and the channel configuration.
Indeed private or group-based channels should always have a restricted
alias. Moreover this alias should check channel members instead of
channel followers, as a channel has members and should not have followers.

This implies a small refactoring of the alias check in the mailgateway.
Code is extracted and moved on alias.mixin class, allowing to tune the
behavior through inheritance.

0 files changed, 0 insertions, 0 deletions