Merge pull request #6385 from Roasbeef/tlv-all-day-err-day

lnrpc: remove legacy onion payload as an option for SendToRoute

docs/release-notes/release-notes-0.15.0.md

@@ -166,6 +166,8 @@ then watch it on chain. Taproot script spends are also supported through the
   to the transaction structure returned from the RPC `GetTransactions` and when
   subscribed with `SubscribeTransactions`.
 
+* [Support for making routes with the legacy onion payload format via `SendToRoute` has been removed.](https://github.com/lightningnetwork/lnd/pull/6385)
+
 ## Database
 
 * [Add ForAll implementation for etcd to speed up

lnrpc/lightning.proto

@@ -2760,7 +2760,7 @@ message Hop {
     TLV format. Note that if any custom tlv_records below are specified, then
     this field MUST be set to true for them to be encoded properly.
     */
-    bool tlv_payload = 9;
+    bool tlv_payload = 9 [deprecated = true];
 
     /*
     An optional TLV record that signals the use of an MPP payment. If present,

lnrpc/routerrpc/router_backend.go

@@ -476,7 +476,7 @@ func UnmarshallHopWithPubkey(rpcHop *lnrpc.Hop, pubkey route.Vertex) (*route.Hop
 		PubKeyBytes:      pubkey,
 		ChannelID:        rpcHop.ChanId,
 		CustomRecords:    customRecords,
-		LegacyPayload:    !rpcHop.TlvPayload,
+		LegacyPayload:    false,
 		MPP:              mpp,
 		AMP:              amp,
 	}, nil