RFC 8414 Section 2 (https://www.rfc-editor.org/rfc/rfc8414#section-2) says code_challenge_methods_supported must be listed to indicate that the authorization server supports PKCE. Doorkeeper only supports plain and S256, so return that if PKCE is enabled.
RFC 8414 Section 2 (https://www.rfc-editor.org/rfc/rfc8414#section-2) says
code_challenge_methods_supported
must be listed to indicate that the authorization server supports PKCE. Doorkeeper only supportsplain
andS256
, so return that if PKCE is enabled.