Put API keys on service model

Similar to how we put templates on the service model, it means less
logic needs to happen in the view code.

app/models/service.py

@@ -1,6 +1,7 @@
 from notifications_utils.field import Field
 from werkzeug.utils import cached_property
 
+from app.notify_client.api_key_api_client import api_key_api_client
 from app.notify_client.billing_api_client import billing_api_client
 from app.notify_client.email_branding_client import email_branding_client
 from app.notify_client.inbound_number_client import inbound_number_client
@@ -335,3 +336,11 @@ class Service():
             template_ids=ids_to_move & self.all_template_ids,
             folder_ids=ids_to_move & self.all_template_folder_ids,
         )
+
+    @cached_property
+    def api_keys(self):
+        return api_key_api_client.get_api_keys(self.id)['apiKeys']
+
+    @property
+    def api_key_names(self):
+        return [key['name'] for key in self.api_keys]