Set which Google Ads account is the user's MCC (My Client Center / manager). This becomes the `login-customer-id` HTTP header for every subsequent Google Ads API call against a sub-account under the manager. Required for agency users with multiple client accounts under one MCC; single-account users normally don't need to call this.
Validates that the customerId is in the user's accessible-accounts list AND that Google Ads reports it as a manager account (`isManager=true`). Pass a sub-account ID and the call rejects.
After setting, the displayed names of sibling sub-accounts in list_ad_accounts will resolve correctly instead of falling back to 'Account 1234567890'.
Connector
Destructive
OAuth