In this commit, we update the RBF state machine to handle early offer
cases. This can happen if after we send out shutdown (to kick things
off), the remote party sends their offer early. This can also happen if
their outgoing shutdown (to ACK ours) was delayed for w/e reason, and we
get their offer first.
The alternative was to modify the state machine itself, but we feel that
handling this early case is better in line with the Robustness principle.
In this commit, we implement the latest version of the RBF loop as
described in the spec. We remove the self loop back based on sending or
receiving shutdown. Instead, from the ClosePending state, we can trigger
a new loop by sending SendOfferEvent (we bump), or OfferReceivedEvent
(they bump).
We also update the rbf state machine w/ the new close addr logic. This
log ensures that the remote party always sends our current address, and
that if they send a new address, we'll update our view of it, and
counter sign the correct transaction.
We also add a CloseErr state. With this new state, we can ensure that
we're able to properly report errors back to the RPC client, and also
optionally force a reconnection or send a warning to the remote party.
In this commit, we enable a custom payer for the rbf coop close. This
allows us to ensure that the party that started one side of the close
flow pays the fees.
In this commit, we add the state transitions for the new protofsm based
RBF chan closer. The underlying protocol is a new asymmetric co-op close
process, wherein either side can initiate a chan closer, and use their
settled funds to pay for fees within the channel.
