Incorrect signature verification in django-ses

Django-SES is a drop-in mail backend for Django. The django_ses library implements a mail backend for Django using AWS Simple Email Service. The library exports the `SESEventWebhookView class` intended to receive signed requests from AWS to handle email bounces, subscriptions, etc. These requests are signed by AWS and are verified by django_ses, however the verification of this signature was found to be flawed as it allowed users to specify arbitrary public certificates. This issue was patched in version 3.5.0.