[REM] mail: remove 'message_last_post' mechanism

Thread mixin class adds a message_last_post field. This field may be
updated when a comment is posted, depending on a context key. Since a
while this context key is not used anymore. This means the field is never
updated. As it is used only as a filter in project we decided to remove
it.

This commit remove the field and the context key support. This kind of
specific feature can be done using customization if necessary in some
advanced use case.

0 files changed, 0 insertions, 0 deletions