This adds the new `payment_metadata` to `RecipientOnionFields`,
passing the metadata from BOLT11 invoices through the send pipeline
and finally copying them info the onion when sending HTLCs.
This completes send-side support for the new payment metadata
feature.
This adds support for setting the new payment metadata field in
BOLT11 invoices, using a new type flag on the builder to enforce
transition correctness.
We allow users to set the payment metadata as either optional or
required, defaulting to optional so that invoice parsing does not
fail if the sender does not support payment metadata fields.
This adds support for reading the new `PaymentMetadata` BOLT11
invoice field, giving us access to the `Vec<u8>` storing arbitrary
bytes we have to send to the recipient.
This commit updates the way that we choose our preferred channel per
counterparty when selecting route hints. Previously, we would choose
the largest usable channel above our requested minimum.
This change updates selection to prefer the smallest channel above the
minimum amount (if provided, plus a scaling factor of 10% to allow
some margin for error). This is the off chain version of not "grinding
our change" - we want to supply route hints for channels that have
enough inbound to facilitate the receive, but not overload our high
inbound channels with smaller payments (since we may need this large
chunk of inbound for larger payment later on).
If there is no minimum amount provided, we err on the side of caution
and just select our highest inbound channels so that payments of any
size have a chance of succeeding. Likewise, if we have no channels above
the minimum, we select the largest channel to maximize our changes of
receiving the payment in multiple parts.
This moves the public payment sending API from passing an explicit
`PaymentSecret` to a new `RecipientOnionFields` struct (which
currently only contains the `PaymentSecret`). This gives us
substantial additional flexibility as we look at add both
`PaymentMetadata`, a new (well, year-or-two-old) BOLT11 invoice
extension to provide additional data sent to the recipient.
In the future, we should also add the ability to add custom TLV
entries in the `RecipientOnionFields` struct.
This is largely motivated by some follow-up work for anchors that will
introduce an event handler for `BumpTransaction` events, which we can
now include in this new top-level `events` module.
If we have a public channel which doesn't yet have six
confirmations the network can't possibly know about it as we cannot
have announced it yet. However, because we refuse to include
route-hints if we have any public channels, we will generate
invoices that no one can pay.
Thus, if we have any public, not-yet-announced channels, include
them as a route-hint.
