API Changes
===========

 * Payment sending methods now take an explicit `PaymentId`, which acts as an
   idempotency token. You may use the PaymentHash for this, which existing
   `InvoicePayer` send methods do, new `_with_id` variants were added (#XXXX).
 * Pending outbound payments are no longer automatically timed-out a few blocks
   after failure. Thus, in order to avoid leaking memory, you MUST call
   `ChannelManager::abandon_payment` when you no longer wish to retry (#XXXX).

Serialization Compatibility
===========================

 * When downgrading to a version of LDK prior to THIS_VERSION_XXX when there are
   resolved payments waiting for a small timeout, the payments may not be
   removed, preventing payments with the same `PaymentId`.