I forked your project and added the following to be able to create new users through the api.
def create_user(self, user_name=None, headers=None):
_data = {}
if user_name is not None:
_data['schemas'] = ["urn:ietf:params:scim:schemas:core:2.0:User"]
_data['userName'] = user_name
_data['entitlements'] = [{'value': 'allow-cluster-create'}]
return self.client.perform_query('POST', '/preview/scim/v2/Users', data=_data, headers=headers)
Of course it can be improved to allow to pass groups and so on. Just in case you want it.