This commit repalces the htlcResolution struct with an interface.
This interface is implemeted by failure, settle and accept resolution
structs. Only settles and fails are exported because the existing
code that handles htlc resolutions uses a nil resolution to indicate
that a htlc was accepted. The accept resolution is used internally
to report on the resolution result of the accepted htlc, but a nil
resolution is surfaced. Further refactoring of all the functions
that call NotifyExitHopHtlc to handle a htlc accept case (rather than
having a nil check) is required.
This commit moves handling of invoice not found
errors into NotifyExitHopHtlc and exposes a
resolution result to the calling functions. The
intention of this change is to make calling
functions as naive of the invoice registry's
mechanics as possible.
When NotifyExitHopHtlc is called and an invoice
is not found, calling functions can take action
based on the HtlcResolution's InvoiceNotFound
outcome rather than having to add a special error
check on every call to handle the error.
This commit adds the resolution result obtained
while updating an invoice in the registry to
htlcResolution. The field can be used by calling
functions to determine the outcome of the
update and act appropriately.
This commit adds a constructor for HtlcResolution creation
to enforce provision of all relevant values when an
event is created. A custom construstor which also takes
a preimage is added for settle events.
This commit renames HodlEvent to HtlcResolution
to better reflect the fact that the struct is
only used for htlc settles and cancels, and that
it is not specifically used for hodl invoices.
With the introduction of additional payload fields for mpp, it becomes
a necessity to have their values available in the on-chain resolution
flow. The incoming contest resolver notifies the invoice registry of the
arrival of a payment and needs to supply all parameters for the registry
to validate the htlc.
This commit modifies hodl htlc notification from invoice registry from a
single notification per hash to distinct notifications per htlc. This
prepares for htlc-specific information (accept height) to be added to the
notification.
