ErrRejectPacket should be returned in PubAck per v5 spec

[SimonMacIntyre]

server/server.go

Lines 911 to 912 in 8f52b89

	} else if errors.Is(err, packets.ErrRejectPacket) {
	return nil

The above behaviour is wrong for v5 spec. Currently if this packet code is assigned to a packet from OnPublish on some custom logic based failure, the expected and desired behaviour is for the ErrRejectPacket to be the reason code used in the PubAck. You can see this in v5 spec here.

Mochi ref to the code:

server/packets/codes.go

Line 95 in 8f52b89

ErrRejectPacket = Code{Code: 0x83, Reason: "packet rejected"}

[SimonMacIntyre]

If maintainers can confirm/agree, I don't mind tackling the PR 🙏

[thedevop]

Thanks @SimonMacIntyre , this makes sense. Please submit a PR.

[SimonMacIntyre]

I haven't forgotten, it's in my todo list :D

If it's urgent to anyone else which seems unlikely, feel free but I should get to this in the next week or two!