Refactor to avoid duplicated method definitions

Each of these methods does the same thing, so this refactors into an
attribute lookup, which saves writing boilerplate code and makes it
easier to add new properties.

app/notify_client/models.py

@@ -265,73 +265,32 @@ class AnonymousUser(AnonymousUserMixin):
 
 class Service(dict):
 
+    ALLOWED_PROPERTIES = {
+        'active',
+        'branding',
+        'dvla_organisation',
+        'email_branding',
+        'email_from',
+        'id',
+        'inbound_api',
+        'letter_contact_block',
+        'message_limit',
+        'name',
+        'organisation_type',
+        'permissions',
+        'prefix_sms',
+        'research_mode',
+        'service_callback_api',
+    }
+
     def __init__(self, _dict):
         # in the case of a bad request current service may be `None`
         super().__init__(_dict or {})
 
-    @property
-    def id(self):
-        return self['id']
-
-    @property
-    def name(self):
-        return self['name']
-
-    @property
-    def inbound_api(self):
-        return self['inbound_api']
-
-    @property
-    def callback_api(self):
-        return self['callback_api']
-
-    @property
-    def service_callback_api(self):
-        return self['service_callback_api']
-
-    @property
-    def organisation_type(self):
-        return self['organisation_type']
-
-    @property
-    def active(self):
-        return self['active']
-
-    @property
-    def message_limit(self):
-        return self['message_limit']
-
-    @property
-    def email_branding(self):
-        return self['email_branding']
-
-    @property
-    def email_from(self):
-        return self['email_from']
-
-    @property
-    def letter_contact_block(self):
-        return self['letter_contact_block']
-
-    @property
-    def prefix_sms(self):
-        return self['prefix_sms']
-
-    @property
-    def research_mode(self):
-        return self['research_mode']
-
-    @property
-    def branding(self):
-        return self['branding']
-
-    @property
-    def dvla_organisation(self):
-        return self['dvla_organisation']
-
-    @property
-    def permissions(self):
-        return self['permissions']
+    def __getattr__(self, attr):
+        if attr in self.ALLOWED_PROPERTIES:
+            return self[attr]
+        raise AttributeError
 
     @property
     def trial_mode(self):