The objective of this commit is to make paymentDescriptor a private
data structure so we can quarantine it to the lnwallet package.
To accomplish this we had to prevent it from leaking out via the
arguments or return values of the public functions in lnwallet.
This naturally had consequences for the htlcswitch package as we
choose other mechanisms for tracking the data that paymentDescriptor
was responsible for.
Astoundingly, this was highly successful and allowed us to remove
a ton of redundant code. The diff for this commit represents a
substantial reduction in total lines of code as well as extraneous
arguments and return values from key functions.
This also sets the stage for future commits where we actually will
be attempting to rid lnwallet of paymentDescriptor completely.
Here we add a function that is capable of recovering LogUpdates from
paymentDescriptors and we refactor the lnwallet code to use this
rather than doing JIT inline construction of the LogUpdates.
In this commit we track the ChannelID on the PaymentDescriptor.
This will be useful in upcoming commits that need to be able to
reconstruct lnwire.Message values from PaymentDescriptors as the
Messages that are exchanged to update channel state all include
the ChannelID.
In this commit, we add a TLV blob to the PaymentDescriptor struct. We also now thread through this value from the UpdateAddHTLC message to the PaymentDescriptor mapping, and the other way around.
