No class for v3applicationcredential auth

[Andrew Berezovskiy]

https://github.com/openstack/python-keystoneclient/tree/master/keystoneclient/auth/identity/v3 is missing a class to perform a v3applicationcredential with the credentials obtained with the Application Credentials page in Horizon.

[Colleen Murphy (krinkle)]

Using keystoneclient for auth is deprecated:

https://docs.openstack.org/python-keystoneclient/latest/using-api-v3.html#non-session-authentication-deprecated

You should use a keystoneauth session instead, which does support v3applicationcredential:

https://docs.openstack.org/keystoneauth/latest/plugin-options.html#v3applicationcredential

[Andrew Berezovskiy (an9rew)]

Thank you, Colleen!