Allow forwarding to unannounced channels if LSP service is enabled

Previously, we'd always disallow forwarding to unannounced channels.
However, if we're acting as an LSP, we *should* allow forwarding to
unannounced channels.

Author: tnull

src/builder.rs

@@ -1090,6 +1090,9 @@ fn build_with_store_internal(
 		// If we act as an LSPS2 service, we need to to be able to intercept HTLCs and forward the
 		// information to the service handler.
 		user_config.accept_intercept_htlcs = true;
+
+		// If we act as an LSPS2 service, we allow forwarding to unnannounced channels.
+		user_config.accept_forwards_to_priv_channels = true;
 	}
 
 	let message_router =