Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Removed unnecassary logic

Added missing 'the'

Fix case

Fixed specs

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

* Created a force=true param that will continue with the previous
  behaviour of the unsubscribe method
* Created a filter for not-logged users so they see a unsubsribe
  confirmation page
* Added the List-Unsubscribe header on emails so the email client can
  display it on top