Merge pull request #9240 from carlaKC/9166-mergeonly

htlcswitch: merge htlc custom records on modify

docs/release-notes/release-notes-0.19.0.md

@@ -105,6 +105,10 @@
     * `lncli abandonchannel` (`Lightning.AbandonChannel` RPC)
     * `lncli restorechanbackup` (`Lightning.RestoreChannelBackups` RPC)
     * `lncli verifychanbackup` (`Lightning.VerifyChanBackup` RPC)
+* The `ForwardInterceptor`'s `MODIFY` option will
+  [merge](https://github.com/lightningnetwork/lnd/pull/9240) any custom
+  range TLVs provided with the existing set of records on the HTLC,
+  overwriting any conflicting values with those supplied by the API.
 
 ## lncli Updates
 
@@ -189,4 +193,4 @@ The underlying functionality between those two options remain the same.
 * Oliver Gugger
 * Pins
 * Viktor Tigerström
-* Ziggie
+* Ziggie