Support HTTP/3

[akiradeveloper]

Tonic will support HTTP/3 which is a efficient protocol on top of QUIC transport IIUC. I don't know this will benefit to Raft but should be (optionally) supported.

hyperium/tonic#339

gRPC over HTTP/3

• https://medium.com/safetycultureengineering/grpc-over-http-3-53f41fc0761e
• Support gRPC over HTTP/3 grpc/grpc#19126

[akiradeveloper]

It would be a great help if I could know prior what design change is to come with tonic's HTTP/3 support. This will affect every design choice in my library.