add simple case and series size display

generic/models.py

@@ -336,6 +336,8 @@ class SeriesBase(models.Model):
         choices=SeriesModifiedChocies.choices,
     )
 
+    total_image_size = models.BigIntegerField(null=True, blank=True, help_text="Stores a (cached) total size of images within the series")
+
     class Meta:
         abstract = True
 
@@ -531,7 +533,14 @@ class SeriesBase(models.Model):
             i.save()
             n = n + 1
 
-    def get_total_image_size(self):
+    def get_total_image_size(self, refresh=False):
+        """Returns the total size of all images in the series.
+        
+        If refresh is set to True the size will be recalculated and saved to the database
+        (in the field 'total_image_size')."""
+        if not refresh and self.total_image_size:
+            return self.total_image_size
+
         images = self.images.filter(removed=False)
 
         size = 0
@@ -539,6 +548,9 @@ class SeriesBase(models.Model):
         for i in images:
             size += i.get_file_size()
 
+        self.total_image_size = size
+        self.save()
+
         return size
 
     def anonymise_images(self):