feat: Completely rework notification framework

This change is needed as
a) there are many different types of notifications. A notification about a new comment does not only relate the comment but also adoption notice and a user that made the comment. Therefore, I introduce a new general notification that has optional links to other objects.
b) this change allows to define a different representation of e-mails vs. display on the website. The new notification type is in charge of representation from now on. Title and text will be deprecated and eventually removed

src/fellchensammlung/receivers.py

@@ -1,23 +1,22 @@
 from django.db.models.signals import post_save
 from django.dispatch import receiver
-from fellchensammlung.models import BaseNotification, CommentNotification, User, TrustLevel, RescueOrganization
+from fellchensammlung.models import Notification, User, TrustLevel, RescueOrganization, \
+    NotificationTypeChoices
 from .tasks import task_send_notification_email
 from notfellchen.settings import host
 from django.utils.translation import gettext_lazy as _
 
 
-@receiver(post_save, sender=CommentNotification)
-def comment_notification_receiver(sender, instance: BaseNotification, created: bool, **kwargs):
-    base_notification_receiver(sender, instance, created, **kwargs)
-
-
-@receiver(post_save, sender=BaseNotification)
-def base_notification_receiver(sender, instance: BaseNotification, created: bool, **kwargs):
-    if not created or not instance.user.email_notifications:
+@receiver(post_save, sender=Notification)
+def base_notification_receiver(sender, instance: Notification, created: bool, **kwargs):
+    print("Dada")
+    if not created or not instance.user_to_notify.email_notifications:
         return
     else:
+        print("Dodo")
         task_send_notification_email.delay(instance.pk)
 
+
 @receiver(post_save, sender=RescueOrganization)
 def rescue_org_receiver(sender, instance: RescueOrganization, created: bool, **kwargs):
     if instance.location:
@@ -40,5 +39,9 @@ def notification_new_user(sender, instance: User, created: bool, **kwargs):
     link_text = f"Um alle Details zu sehen, geh bitte auf: {user_url}"
     body_text = new_user_text + user_detail_text + link_text
     for moderator in User.objects.filter(trust_level__gt=TrustLevel.MODERATOR):
-        notification = BaseNotification.objects.create(title=subject, text=body_text, user=moderator)
+        notification = Notification.objects.create(title=subject,
+                                                   text=body_text,
+                                                   notification_type=NotificationTypeChoices.NEW_USER,
+                                                   user_to_notify=moderator,
+                                                   user_related=instance)
         notification.save()