'Must return user details in a know internal struct:
{\'username\': <username if any>,
\'email\': <user email if any>,
\'fullname\': <user full name if any>,
\'first_name\': <user first name if any>,
\'last_name\': <user last name if any>}'

def get_user_details(self, response):

    raise NotImplementedError('Implement    in    subclass')
