add some `client-secret` required tips when `python manage.py createapplication` in version >= 2.0.0

[undo-nothing]

Is your feature request related to a problem? Please describe.
when i createapplication like before using python manage.py createapplication --name self-front-end --client-id=self-front-end confidential password, than copy client_id and client_secret use in basic auth, response is "invalid_client".
i debug and find client_secret is use django check_password . and need provide source client_secret in python manage.py createapplication like python manage.py createapplication --name self-front-end --client-id=self-front-end --client-secret=123456 confidential password.

i think it is better add a tip when i createapplication, if not got --client-secret=123456 return a tips.

Describe the solution you'd like
when createapplication, if not got --client-secret=123456 return a tips.

@n2ygk