The clients never get passed useful values to their `__init__` methods.
Rather the real values are passed through later using the `init_app`
method.
So it should be an error if the client is relying on the values that
get passed to it’s init method. Easiest way to ensure this is by making
the `__init__` method not expect any arguments and passing fake values
to the `Super` call.
Mutating dictionaries is gross and doesn’t work as you’d expect. Better
to have the function return a new dictionary instead.
Means we can be explicit that `created_by` is one of the allowed params
when updating a service.
