post
https://api.zenskar.com/customers//payment_methods/attach
Attaches an external payment method (from Stripe or other provider) to a customer. Connector Auto-Detection:
- If 'connector' is not provided, the system will automatically detect the connector by querying resource mappings
- If exactly one connector mapping exists for the customer, it will be used automatically
- If multiple connector mappings exist, you must explicitly specify which connector to use
- If no connector mappings exist, an error will be returned
