square.onCustomerCustomAttributeDefinitionOwnedCreated subscribes to customer.custom_attribute_definition.owned.created for the selected seller. It requires CUSTOMERS_READ.
Example
automations/square-on-customer-custom-attribute-definition-owned-created.automation.ts
Event
A custom attribute definition was created by your application. The application that created the custom attribute definition is the owner of the definition and corresponding custom attributes. This event replaces the deprecated customer.custom_attribute_definition.created event. The signal resolves to the officialSquare.CustomerCustomAttributeDefinitionOwnedCreatedEvent payload with type narrowed to customer.custom_attribute_definition.owned.created.