Sync a product feed to Google via the Merchant API (successor to Content API for Shopping)

Steps

1. Use the Merchant API (v1), which is now generally available and the official successor to the Content API for Shopping; the Content API for Shopping is scheduled for shutdown on August 18, 2026.
2. Authenticate with OAuth 2.0 using a service account or user OAuth flow with the `https://www.googleapis.com/auth/content` scope.
3. Insert or update products by calling `POST https://merchantapi.googleapis.com/products/v1beta/accounts/{merchantId}/products` (or the v1 equivalent); provide structured product data including GTIN, brand, condition, availability, price, and required attributes for the target country.
4. For bulk operations, use the Products API batch endpoint or the DataSources API to register a supplemental feed and trigger a fetch from a hosted URL.
5. Poll the product status via `GET /products/{productId}` and inspect the `productStatuses` to check for disapprovals, warnings, and whether the product is active in Google Shopping.
6. Monitor feed health in the Merchant Center UI or via the `productstatuses.list` endpoint; address disapproval reasons (missing GTIN, image policy violations, price mismatches) before re-submitting.