[Openid-specs-fapi] Issue #393: Additional metadata in authorization details (openid/fapi)

[Kosuke Koiwai]

New issue 393: Additional metadata in authorization details
https://bitbucket.org/openid/fapi/issues/393/additional-metadata-in-authorization

Kosuke Koiwai:

In [PR249](https://bitbucket.org/openid/fapi/pull-requests/249/grant-management-refactoring-alternative#comment-209981950), we discussed that clients may want to know how and when the user granted it. 

It would be useful to have

* amr/acr
* auth\_time

any other suggestions?

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