Google Sheet Adapter

New Google Sheet adapter docs — look up customers from a CSV file hosted in Google Drive.

Added

• Google Sheet adapter — full documentation for getCustomerDetails (and its getCustomerDetailsCSV alias), including phone-based and ID-based lookups, filterField/filterValue narrowing, the crmConfig field mapping (customers_csv_*), how the 10-minute refresh works, how to update the customer list (upload a new CSV — don't edit in place), and supported phone formats