[Openid-specs-fapi] Issue #536: Discovery should be mandated for clients (openid/fapi)

[josephheenan]

New issue 536: Discovery should be mandated for clients
https://bitbucket.org/openid/fapi/issues/536/discovery-should-be-mandated-for-clients

Joseph Heenan:

As noted in [https://bitbucket.org/openid/fapi/issues/525/decide-on-what-to-do-for-a-cuckoo-s-token#comment-63894845](https://bitbucket.org/openid/fapi/issues/525/decide-on-what-to-do-for-a-cuckoo-s-token#comment-63894845) the current FAPI2 profile requires OPs to support discovery but does not mandate RPs to use discovery.

I believe this was an accidental omission and we should mandate RPs use discovery.