Use new fields for getting orgs and services

Uses https://github.com/alphagov/notifications-api/pull/2539 to reduce
the number of API calls we make.

app/models/__init__.py

@@ -12,6 +12,12 @@ class JSONModel():
     def __bool__(self):
         return self._dict != {}
 
+    def __hash__(self):
+        return hash(self.id)
+
+    def __eq__(self, other):
+        return self.id == other.id
+
     def __getattr__(self, attr):
         if attr in self.ALLOWED_PROPERTIES:
             return self._dict[attr]