Add Logging or Document Webhook Deletion Behavior

[tomozilla]

The Pay::Webhook#process! method deletes webhook records after processing, but this isn't logged, which can make debugging or auditing difficult.

Adding a log entry like: Rails.logger.info "Deleted webhook ID: #{id}, event_type: #{event_type}".
Updating the documentation to explain the default deletion behavior.
This would clarify the gem's behavior and assist developers in customizing or debugging as needed.