Enhance the payment sheet DX

[thorsten-stripe]

You can initPaymentSheet with bad params and it either crashes or does not validate and return an error. Validating the params passed and ensuring a developer-friendly error message is returned is vital as it helps users self-serve to correct themselves.

• Case A: pass customerEphemeralKeySecret: “123” on initPaymentSheet(), the SDK does not return an error, instead tries to present PaymentSheet then dismisses. Really hard for a user to debug and self help as there’s no error message. A support interaction of a user running into this issue zendesk link and second Zendesk link where the user passes a publishable key instead of EphemeralKey secret.
• Case B pass paymentIntentClientSecret: “abc”, no validation, instead app just crashes.
• Case c pass dummy customerId, above, app crashes.
• Case d) pass a valid ephemeral key, but no customer param, app crashes.

@arekkubaczkowski please investigate whether the native SDKs can take care of any of this, and how we can prevent the crashes.