This commit extends the forward HTLC intercept response with fields that
can be used in conjunction with a `ResumeModified` action to modify the
intercepted HTLC p2p message.
Introduce `ResumeModified` action to resume standard behavior of a p2p
message with optional modifications as specified by the client during
interception.
- Introduce the field `CustomRecords` to the type `UpdateAddHtlc`.
- Encode and decode the new field into the `ExtraData` field of
the `update_add_htlc` wire message.
This commit introduces the `CustomRecords` type in the `lnwire` package,
designed to hold arbitrary byte slices. Each entry in this map can
associate with TLV type values that are greater than or equal to 65536.
As is, we can't use PackRecords when some data may already be stored in the ExtraData field. To allow this use case, we add a failing test, then modify `PackRecords` to append the existing raw bytes (prepend the new records).
Note that this doesn't 100% solve the problem, as for the stream to be cannonical we need unique IDs/types and also for them to be in ascending order.
In this commit, we start to use the new AuxSigner to obtain+verify aux sigs for all second level HTLCs. This is similar to the existing SigPool, but we'll only attempt to do this if the AuxSigner is present (won't be for most channels).
In this commit, we add a new aux signer interface that's meant to mirror the SigPool. If present, this'll be used to (maybe) obtain signatures for second level HTLCs for certain classes of custom channels.
For the initiator, once we get the signal that the PSBT has been
finalized, we'll call into the aux funder to get the funding desc. For
the responder, once we receive the funding_created message, we'll do the
same.
We now also have local+remote aux leaves for the commitment transaction.
In this commit, we modify the aux funding work flow slightly. We won't
be able to generate the full AuxFundingDesc until both sides has
sent+received funding params. So we'll now only attempt to bind the
tapscript root as soon as we send+recv the open_channel message.
We'll now also make sure that we pass the tapscript root all the way
down into the musig2 session creation.
In this commit, we make a new `AuxFundingController` interface capable of processing messages off the wire. In addition, we can use it to abstract away details w.r.t how we obtain a `AuxFundingDesc` for a given channel.
We'll now use this whenever we get a channel funding request, to make sure we pass along the custom state that a channel may require.
This struct will house all the information we'll need to do a class of custom channels that relies primarily on adding additional items to the tapscript root of the HTLC/commitment/funding outputs.
This lets us get rid of the mutex usage there. We also shift the algo slightly to increment by 1, then use that as the next value, which plays nicer with the atomics.
With this commit, we allow the `MsgRouter` to be available in the `ImplementationCfg`. With this, programs outside of lnd itself are able to now hook into the message processing flow to direct handle custom messages, and even normal wire messages.
