Add validate-only and sandbox testing for Google Business Profile management

Please add a non-mutating testing mode for the Google Business Profile management endpoints.

Google’s Business Information API supports validateOnly=true for location updates, but Zernio’s PUT /v1/accounts/{accountId}/gmb-location-details currently does not expose it. Please forward or expose validateOnly for location updates.

It would also be helpful to provide a Zernio-side dry-run mode for GBP operations that do not have a Google validation-only option, including:

• food menus

• attributes

• media uploads and deletions

• place action links

The dry run should validate the exact request, resolve the connected account and location, check capabilities and permissions, and return the payload or diff that would be sent without changing the live Google listing.

A dedicated GBP sandbox or documented test-account approach would also be useful. At present, staging integrations connected to a real GBP listing can still make live changes, which makes safe end-to-end testing difficult.