[Openid-specs-ab] Issue #2080: Metadata declaring the historical keys endpoint location (openid/connect)

[mbj]

New issue 2080: Metadata declaring the historical keys endpoint location
https://bitbucket.org/openid/connect/issues/2080/metadata-declaring-the-historical-keys

Michael Jones:

The historical keys endpoint is currently at `<EntityIdentifier>/.well-known/openid-federation-historical-jwks`. It would have been more consistent to publish its location in the Entity's metadata for the `federation_entity` Entity Type in a `federation_historical_keys_endpoint` property. I recommend that we do that.

Note that this need not be a breaking change to implementations in practice.  If a deployment publishes a `federation_historical_keys_endpoint` metadata entry with the value `<EntityIdentifier>/.well-known/openid-federation-historical-jwks`, then clients locating the endpoint either the old way or the new way will continue to work.

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