[Openid-specs-fapi] Issue #377: grant_id_required client metadata (openid/fapi)

[Takahiko Kawasaki]

New issue 377: grant_id_required client metadata
https://bitbucket.org/openid/fapi/issues/377/grant_id_required-client-metadata

Takahiko Kawasaki:

I don't think that it is worth defining the `grant_id_required` client metadata. Clients can just ignore `grant_id` in a token response if they do not need it in the same way as they ignore `refresh_token`.