Capture additional Stripe webhook events

Instead of using checkout.session.completed, we should probably use the following:

• payment_intent.canceled: Occurs when a PaymentIntent is canceled.
• payment_intent.payment_failed: Occurs when a PaymentIntent has failed the attempt to create a payment method or a payment.
• payment_intent.succeeded: Occurs when a PaymentIntent has successfully completed payment.

This way, we capture all the relevant activities of a payment in our system.