json: reverse parse a coin_mvt tag back into an enum

common/json_helpers.c

@@ -108,6 +108,22 @@ bool json_to_channel_id(const char *buffer, const jsmntok_t *tok,
 			  cid, sizeof(*cid));
 }
 
+
+bool json_to_coin_mvt_tag(const char *buffer, const jsmntok_t *tok,
+			  enum mvt_tag *tag)
+{
+	enum mvt_tag i_tag;
+	for (size_t i = 0; i < NUM_MVT_TAGS; i++) {
+		i_tag = (enum mvt_tag) i;
+		if (json_tok_streq(buffer, tok, mvt_tag_str(i_tag))) {
+			*tag = i_tag;
+			return true;
+		}
+	}
+
+	return false;
+}
+
 bool split_tok(const char *buffer, const jsmntok_t *tok,
 				char split,
 				jsmntok_t *a,