Typo
Update conversations to allow group conversations
* Make the Conversation store its hash to be unique once created
* Make impossible to create more than one two-people conversations with the same users
* Updated tests
Filter user activities list by verb:post
Remove unneded ELLIPSIS comments on doctests
Allow to override unsubscribe permission default
Filter conversation messages from user activities
Fix variable redefinition in comprehension list
refactor models WIP