suggested certification test for post quantum preparation - unparseable keys in server jwks

[jogu]

As discussed on today's FAPI WG call - see openid/connect#2147

Suggest adding a similar test to the FAPI1/FAPI2/FAPI-CIBA client tests, which would need WG approval as it would probably result in a hard-fail for non-compliant clients (the test would fail to complete due to the client aborting), whereas the spec text is only a 'should'.

[dpostnikov]

No objections to today's Atlantic call to proceed with the test change.

[davetonge-mh]

Discussed again, and again no objections