PostForm: Save supported headers in obj metadata (#3474)

Supported Headers like Content-Type, Cache-Control, Content-Encoding, X-Amz-* , etc.. are now saved in object metadata

cmd/bucket-handlers.go

@@ -429,9 +429,8 @@ func (api objectAPIHandlers) PostPolicyBucketHandler(w http.ResponseWriter, r *h
 		}
 	}
 
-	// Save metadata.
-	metadata := make(map[string]string)
-	// Nothing to store right now.
+	// Extract metadata to be saved from received Form.
+	metadata := extractMetadataFromForm(formValues)
 
 	sha256sum := ""