watchtower/wtdb: add Encode/Decode methods to wtclient structs

channeldb/codec.go

@@ -103,6 +103,11 @@ func WriteElement(w io.Writer, element interface{}) error {
 			return err
 		}
 
+	case lnwire.ChannelID:
+		if _, err := w.Write(e[:]); err != nil {
+			return err
+		}
+
 	case uint64:
 		if err := binary.Write(w, byteOrder, e); err != nil {
 			return err
@@ -259,6 +264,11 @@ func ReadElement(r io.Reader, element interface{}) error {
 		}
 		*e = lnwire.NewShortChanIDFromInt(a)
 
+	case *lnwire.ChannelID:
+		if _, err := io.ReadFull(r, e[:]); err != nil {
+			return err
+		}
+
 	case *uint64:
 		if err := binary.Read(r, byteOrder, e); err != nil {
 			return err