HTTP_AUTH_USERNAME and HTTP_AUTH_PASSWORD to enable HTTP Basic Auth,
or DISABLE_AUTH_WARNING to hide this warning.
A source is a separate inbox for tracking email events. Each source has its own webhook URL that you'll configure in AWS.
We suggest starting with one source per project. Later, if you want to track different types of emails separately, you can create additional sources. For example, one for transactional emails (password resets, receipts) and another for marketing emails (newsletters, promotions).