Change mapit url to accomodate unit_id codes

Author: GeoWill

every_election/apps/organisations/models/divisions.py

@@ -127,10 +127,10 @@ def format_geography_link(self):
         except (ValueError, AttributeError):
             return None
 
-        if code_type.lower() != "gss":
+        if code_type.lower() not in ("gss", "unit_id"):
             return None
 
-        return "https://mapit.mysociety.org/area/{}".format(code)
+        return f"https://mapit.mysociety.org/code/{code_type}/{code}"
 
 
 class DivisionGeography(models.Model):