Add DAO function to archive a user

For a user to be able to be archived, each service that they are a
member of must have at least one other user who is active and who has
the 'manage-settings' permission.

To archive a user we remove them from all their services and
organisations, remove all permissions that they have and change some of
their details:
- email_address will start with '_archived_<date>'
- the current_session_id is changed (to sign them out of their current
session)
- mobile_number is removed (so we also need to switch their auth type to
email_auth)
- password is changed to a random password
- state is changed to 'inactive'

If any of the steps fail, we rollback all changes.

app/models.py

@@ -137,8 +137,14 @@ class User(db.Model):
     def check_password(self, password):
         return check_hash(password, self._password)
 
-    def get_permissions(self):
+    def get_permissions(self, service_id=None):
         from app.dao.permissions_dao import permission_dao
+
+        if service_id:
+            return [
+                x.permission for x in permission_dao.get_permissions_by_user_id_and_service_id(self.id, service_id)
+            ]
+
         retval = {}
         for x in permission_dao.get_permissions_by_user_id(self.id):
             service_id = str(x.service_id)