Signed transaction data object

[senexi]

Currently the transaction_data object is defined as a "base64url encoded JSON object". For some use-cases it might be useful to actually sign this data, so it can later be linked to its originator. So the idea would be to also allow an encoded JWT here.

[jogu]

Hi @senexi , can you confirm if you've signed an OpenID contribution agreement please, and if not sign one please? https://openid.net/intellectual-property/openid-foundation-contribution-agreements/

Thanks!