The Notify API client changed in version 4 to take two arguments, not
three (service ID was removed in favour of the combined API key).
This gets a bit gnarly because the API key has to be at least a certain
length so it can be substringed internally.
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.
