draft-ietf-oauth-attestation-based-client-auth-04

• remove key attestation example
• restructured JWT Claims for better readability
• added JOSE typ values for Client Attestation and Client Attestation PoP
• add RATS relation
• add concatenated representation without headers
• add PAR endpoint example
• fix PoP examples to include jti and nonce
• add iana http field name registration