json: Add helper to serialize short_channel_id_dir

We'll need it in the next commit to exclude channels and their directions.

common/json_helpers.c

@@ -3,7 +3,6 @@
 #include <bitcoin/privkey.h>
 #include <bitcoin/psbt.h>
 #include <bitcoin/pubkey.h>
-#include <bitcoin/short_channel_id.h>
 #include <ccan/ccan/str/hex/hex.h>
 #include <common/amount.h>
 #include <common/channel_id.h>
@@ -164,6 +163,18 @@ void json_add_short_channel_id(struct json_stream *response,
 			short_channel_id_outnum(scid));
 }
 
+void json_add_short_channel_id_dir(struct json_stream *response,
+			       const char *fieldname,
+			       const struct short_channel_id_dir *scidd)
+{
+	json_add_member(response, fieldname, true, "%dx%dx%d/%d",
+			short_channel_id_blocknum(&scidd->scid),
+			short_channel_id_txnum(&scidd->scid),
+			short_channel_id_outnum(&scidd->scid),
+			scidd->dir
+		);
+}
+
 void json_add_address(struct json_stream *response, const char *fieldname,
 		      const struct wireaddr *addr)
 {

common/json_helpers.h

@@ -2,6 +2,7 @@
 #ifndef LIGHTNING_COMMON_JSON_HELPERS_H
 #define LIGHTNING_COMMON_JSON_HELPERS_H
 #include "config.h"
+#include <bitcoin/short_channel_id.h>
 #include <bitcoin/tx.h>
 #include <common/json.h>
 #include <wire/wire.h>
@@ -92,6 +93,11 @@ void json_add_short_channel_id(struct json_stream *response,
 			       const char *fieldname,
 			       const struct short_channel_id *id);
 
+/* '"fieldname" : "1234:5:6/7"' */
+void json_add_short_channel_id_dir(struct json_stream *response,
+				   const char *fieldname,
+				   const struct short_channel_id_dir *id);
+
 /* JSON serialize a network address for a node */
 void json_add_address(struct json_stream *response, const char *fieldname,
 		      const struct wireaddr *addr);