• Introduce v2 feature with oblivious, asynchronous, serverless payjoin
• Return RequestContext from which either v1 or v2 (Request, Context) tuples may be extracted
• Derive Debug, Clone from send::Request, receive::UncheckedProposal, optional_parameters::Params
• Don't derive Debug, Clone from uri::{Payjoin, PayjoinParams}
• Derive Serialize, Deserialize for RequestContext and Enrolled in v2 to enable persistent state for asynchronous requests
• UncheckedProposal::check_can_broadcast became ::check_broadcast_suitability allowing receiver to specify minnimum acceptable feerate