htlcswitch: merge copy htlc custom records

lnrpc/routerrpc/router.swagger.json

@@ -1525,7 +1525,7 @@
             "type": "string",
             "format": "byte"
           },
-          "description": "Any custom records that should be set on the p2p wire message message of\nthe resumed HTLC. This field is ignored if the action is not\nRESUME_MODIFIED.\n\nIf this map is populated, it will overwrite any of the wire custom\nrecords set by LND. It is the caller's responsibility to copy any desired\nrecords across. If the map is empty, no action will be taken and existing\ncustom records will be propagated.\n\nThe API does not currently support deleting custom records, unless they\nare overwritten by a new set."
+          "description": "Any custom records that should be set on the p2p wire message message of\nthe resumed HTLC. This field is ignored if the action is not\nRESUME_MODIFIED.\n\nThis map will merge with the existing set of custom records (if any),\nreplacing any conflicting types. Note that there currently is no support\nfor deleting existing custom records (they can only be replaced)."
         }
       },
       "description": "*\nForwardHtlcInterceptResponse enables the caller to resolve a previously hold\nforward. The caller can choose either to:\n- `Resume`: Execute the default behavior (usually forward).\n- `ResumeModified`: Execute the default behavior (usually forward) with HTLC\nfield modifications.\n- `Reject`: Fail the htlc backwards.\n- `Settle`: Settle this htlc with a given preimage."