SMTP Authentication Error when sending emails

When creating a new account, no registration email is sent: the Django container logs show a `Internal Server Error: /users/registration/` following a `smtplib.SMTPAuthenticationError: (535, b'5.7.3 Authentication unsuccessful')`

The accounts/auth module was lifted from another project, where it is battle-tested and works without a hitch. The reason why Django fails to authenticate and send an email here is probably because it runs in a Docker container and does not have access to the email credentials, which are on the server.

Implementation suggestion: use the template folder in the `deployment` repository to put an `.env` file in the `data` folder. It should contain variables like EMAIL_USER and EMAIL_PW that it should interpolate from `bo_deploy.json`. We can also put the Django secret key here.