Response mode parameter values

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The existing parameter response_mode only references that it is defined in RFC 6749, yet this parameter tells the wallet where/how to send the vp_token back to the verifier. This is especially not very clear in section "5.2 Existing Parameters", where only 'direct_post' is mentioned, without leaving syntactic room for other options (such as specified in Appendix "A.2. Request": dc_api). A clarification on the scope and role of this parameter might well be clarifying in this context.