Move data transformation into the form

Follows what we’re doing with the folders stuff. Avoids having too many
very straightforward methods on the model. Especially when the data they
need is only used by the form. So it’s better to encapsulate the logic
in the form.

app/models/service.py

@@ -345,10 +345,6 @@ class Service():
             key=lambda key: key['name'].lower(),
         )
 
-    @property
-    def api_key_names(self):
-        return [key['name'] for key in self.api_keys]
-
     def get_api_key(self, id):
         try:
             return next(key for key in self.api_keys if key['id'] == id)