E2E testing webhook with successful HMAC validation

[gcatanese]

The E2E Testing Suite includes a test to verify the webhook receives the payload and returns 401 (as HMAC Validation fails).

Create a new test that can verify the HMAC signature is valid and the payload can be processed

Note: we need to identify a way to create a valid HMAC signature for running the E2E testing suite

[Kwok-he-Chu]

Closed in #39 #24