Separate parsing StripeEvent from verification

[furkan-guvenc]

Is your feature request related to a problem? Please describe.

In my webhook, I serialize and push the stripe events to a task queue to process them later and to return 200 to Stripe immediately. Then a worker picks up the task, deserialise the event and process it.

Since events are both verified and deserialised in do_construct_event, they are de/serialized twice

Describe the solution you'd like

We can separate verification and deserialisation.

struct VerifiedEventPayload(pub String); // name can change

impl VerifiedEventPayload {
  fn parse_payload(self) -> Result<Event, WebhookError> {
    // Same as `parse_payload` in async-stripe-webhook/src/webhook.rs
  }
}

// in webhook.rs
fn verify_event(
        self,
        payload: String,
        sig: &str,
        secret: &str,
    ) -> Result<VerifiedEventPayload, WebhookError>{
     // Same as `do_construct_event` except the last line `parse_payload`
}

do_construct_event will run verify_event then parse_payload. We need to have construct_event and construct_event_with_timestamp equivalents also. I can open a PR if you would like

Describe alternatives you've considered

No response

Additional context

No response

[arlyon]

Thanks for taking the time. Are you seeing event parsing taking longer than expected, given you don't want to verify them twice? Or is this just a 'correctness' thing? Open to a PR if we can preserve the API surface.

[furkan-guvenc]

I didn't do any benchmarking, it is more of a correctness