LSPS5 Notifications for Pending HTLCs #762
Description
After LDK ships HTLC interception (lightningdevkit/rust-lightning#4300) we'll need to enable it and then use it to send LSPS5 Notifications if the HTLC is to a client. Same goes for onion messages in the onion message mailbox logic. There's a decent amount of wiring things up here, so kinda wondering if there's any ideas for how to make it easier on the rust-lightning side of the house, but sadly I don't really see any :/