Some duplicated code can be removed by using an `if...else` statement.
Some example code (incomplete):

    if self.reissue_refresh_tokens:
        # Execute self.token_generator.create_access_token_data()
    else:
        # Execute self.token_generator.generate()

    # Use the data generated in either the `if` or the `else` block
    access_token = AccessToken(...)
    json_success_response(...)
    return response