Verify blinded keysend payments (Blinded Paths, keysend, Bolt12, Offer)

https://github.com/lightningdevkit/rust-lightning/pull/3383

Host: vincenzopalazzo  -  PR author: valentinewallace

Notes

Question

  1. Did you review ldk/3383? Is it a Concept ACK, approach ACK, tested ACK, or NACK?
  2. What is the goal of this PR, and what is the keysend feature?
  3. What is the difference between keysend and normal invoice payment?
  4. What are static invoices?
  5. In lightning/src/ln/channelmanager.rs why we need has_recipient_created_payment_secret field?
  6. What’s a payment secret? How was it used in LDK prior to the PR?
  7. What does this PR do differently for async payments?