/resources/product_link.proto

--- v14/resources/product_link.proto    2023-10-18 04:25:31.000000000 +0000
+++ v15/resources/product_link.proto    2023-10-18 04:25:35.000000000 +0000
@@ -66,6 +66,10 @@
     // Immutable. Google Ads link.
     GoogleAdsIdentifier google_ads = 5
         [(google.api.field_behavior) = IMMUTABLE];
+
+    // Immutable. Google Merchant Center link.
+    MerchantCenterIdentifier merchant_center = 12
+        [(google.api.field_behavior) = IMMUTABLE];
   }
 }

@@ -91,3 +95,13 @@
     }
   ];
 }
+
+// The identifier for Google Merchant Center account
+message MerchantCenterIdentifier {
+  // Immutable. The customer ID of the Google Merchant Center account.
+  // This field is required and should not be empty when creating a new
+  // Merchant Center link. It is unable to be modified after the creation of
+  // the link.
+  optional int64 merchant_center_id = 1
+      [(google.api.field_behavior) = IMMUTABLE];
+}