Use this method to present the payment method user interface (UI) to the user.
func showPaymentMethod(intent: PrimerSessionIntent)
checkout when you want go through the checkout flow
vault when you want to vault a payment mehtod, so you can use the token to pay another time.
An exception that will be thrown in case method of the manager has been called using unsupported
intent. Supported payment session intents for given payment method are returned in the onAvailablePaymentMethodLoaded delegate.