#169 Team delete-restore

* adds restorable delete functionality to Team model
* refactors minor code model parts by introducing DeletableObjectMixin
* only non-deleted Teams can be chosen for sharing
* deleted Teams can be restored using the proper function on the backend admin
* deleted Teams do not provide
* adds migration

user/models/team.py

@@ -1,10 +1,11 @@
 from django.db import models
 
-from konova.models import UuidModel
+from konova.models import UuidModel, DeletableObjectMixin
 from konova.utils.mailer import Mailer
+from user.models import UserActionLogEntry
 
 
-class Team(UuidModel):
+class Team(UuidModel, DeletableObjectMixin):
     """ Groups users in self managed teams. Can be used for multi-sharing of data
 
     """
@@ -16,6 +17,19 @@ class Team(UuidModel):
     def __str__(self):
         return self.name
 
+    def mark_as_deleted(self, user):
+        """ Creates an UserAction entry and stores it in the correct field
+
+        Args:
+            user (User): The performing user
+
+        Returns:
+
+        """
+        delete_action = UserActionLogEntry.get_deleted_action(user, "Team deleted")
+        self.deleted = delete_action
+        self.save()
+
     def send_mail_shared_access_given_team(self, obj_identifier, obj_title):
         """ Sends a mail to the team members in case of given shared access