[BUG] "setup-production" explains wrong EMAIL_BACKEND values

[Zocker1999NET]

Describe the bug
The documentation setup-production.adoc (rendered) suggests invalid values for EMAIL_BACKEND. To quote:

EMAIL_BACKEND=console  # use an SMTP server or display the emails in the console (either "smtp" or "console")

However, the newest Taiga version fails to send any mails with EMAIL_BACKEND=smtp. The logs from the async container shows a Python import error, stating that smtp is invalid. By further investigation, I discovered that Taiga uses Django's mail backend, which describes correct & working values (e.g. EMAIL_BACKEND=django.core.mail.backends.smtp.EmailBackend).

How can we reproduce the behavior
Launch a Docker Taiga setup with EMAIL_BACKEND=smtp and valid SMTP credentials. Trigger a email notification and look for errors in the taiga-async container logs.

Workarounds
Use documentation from: https://docs.djangoproject.com/en/5.0/topics/email/

Taiga environment
Installed as described in taiga-docker.

Additional context
Neither the code from the Docker container's entrypoint nor from taiga-backend suggest that they use these environment variables. To me it seems that Django's mail backend does access these environment variables directly. Hence, IMO it would make sense to just link to the Django backend instead of copying their documentation into Taiga's documentation.

EDIT: It seems that PR #17 introduced this issue.