とりあえず、一貫性をとるために “checkid_setup_direct” –> “direct_checkid_setup” 。”direct_checkid_immediate”のユースケースはよくわからない。
9.1. Authentication Request Parameters
Authentication Request can be sent directly or indirectly. When it is sent directly, an Artifact is returned, and the Artifact is sent through indirect communication to the OP by 9.1.1 Artifact Authentication Request.
As specified in Section 4.1.2.
or"checkid_setup", "checkid_immediate_direct" or "checkid_setup_direct",“direct_checkid_immediate” or “direct_checkid_setup”.