Make UserStore available in case of PPID as well.

[daisukenishino2]

Requirement

• Support the "PPID". #119
• Examine the point that should be use the PPID extension. #132

[daisukenishino2]

Alternatives

• Make the REST API available.
• Include it only in the assertion that returns the first time.

Memo

• Backlog
• There is possibility that it is not feasible in the first place.