info: add json func to get info struct as json string directly

info/info.go

@@ -1,6 +1,7 @@
 package info
 
 import (
+	"encoding/json"
 	"fmt"
 	"github.com/streamingfast/substreams/manifest"
 	"github.com/streamingfast/substreams/pipeline/outputmodules"
@@ -186,6 +187,19 @@ func Info(manifestPath string, opts ...InfoOption) (*ManifestInfo, error) {
 	return manifestInfo, nil
 }
 
+func InfoJson(manifestPath string, opts ...InfoOption) (string, error) {
+	info, err := Info(manifestPath, opts...)
+	if err != nil {
+		return "", err
+	}
+
+	res, err := json.MarshalIndent(info, "", "  ")
+	if err != nil {
+		return "", err
+	}
+	return string(res), nil
+}
+
 func strPtr(s string) *string {
 	return &s
 }