Modify load site data to be an zone update script for spreadsheet changes

backend/right_tree/api/management/commands/loadsitedata.py

@@ -33,16 +33,25 @@ def load_habitat_zone_data(sheet):
         habitats.add(current_habitat)
         zones.add((current_habitat, current_zone, current_variant, current_refined_variant, col[0].column_letter))
 
-    for habitat in habitats:
-        habitat_obj = Habitat(name=habitat)
-        habitat_obj.save()
+    # Create habitats - generally this is not needed for updating
+    # for habitat in habitats:
+    #     habitat_obj = Habitat(name=habitat)
+    #     habitat_obj.save()
 
     for habitat, zone, variant, refined_variant, col_letter in zones:
-        zone_obj = Zone(name=zone, variant=variant,
-                        refined_variant=refined_variant, habitat=habitat, related_zone_segment=col_letter)
+        
+        # Retrieve existing objects
+        habitat_obj = Habitat.objects.get(name=habitat)
+        zone_obj = Zone.objects.get(related_svg_segment=col_letter)
+        
+        # Update fields if required
+        zone_obj.name = zone
+        zone_obj.variant = variant
+        zone_obj.refined_variant = refined_variant
+        zone_obj.habitat = habitat_obj
+
+        # Save the object
         zone_obj.save()
-
-
 class Command(BaseCommand):
     help = 'Ingests the site spreadsheet data into the database'