Server Messages unpublish

* changes unpublish_on to optional value
* simplifies fetching of server message news

news/models.py

@@ -1,4 +1,5 @@
 from django.db import models
+from django.utils import timezone
 from django.utils.translation import gettext_lazy as _
 
 from konova.models import BaseResource
@@ -22,7 +23,7 @@ class ServerMessage(BaseResource):
     body = models.TextField()
     is_active = models.BooleanField(default=True)
     publish_on = models.DateTimeField()
-    unpublish_on = models.DateTimeField()
+    unpublish_on = models.DateTimeField(null=True, blank=True)
     importance = models.CharField(max_length=100, choices=ServerMessageImportance.choices)
 
     def save(self, user=None, *args, **kwargs):
@@ -34,3 +35,24 @@ class ServerMessage(BaseResource):
                 self.modified = UserActionLogEntry.get_edited_action(user)
 
         super().save(*args, **kwargs)
+
+    @staticmethod
+    def get_current_news():
+        """ Getter for the most current news
+
+        Meaning the ones that are
+            * activated
+            * publish_on has passed
+            * unpublish_on (if set) has not been passed, yet
+
+        """
+        now = timezone.now()
+        news = ServerMessage.objects.filter(
+            is_active=True,
+            publish_on__lte=now,
+        ).exclude(
+            unpublish_on__lte=now,
+        ).order_by(
+            "-publish_on"
+        )
+        return news