Design negotiation mechanism for prop324
Based on discussion with @mikeperry, I'm going to try to get the negotiation mechanisms for prop324 (rtt congestion) figured out this week.
AFAIK what needs to get agreed upon between the client and the relay are:
- Will be we using xon/xoff or stream sendmes?
- What is the circuit SENDME window?
Also we may need to figure out how an onion service advertises support for this protocol.