Reintroduce missed docker secret handling

[PromoFaux]

What does this PR aim to accomplish?:

The V6 image was rebuilt from scratch - and this feature was accidentally missed.

Reproduces functionality of #584

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[yubiuser]

Why did you merge this so quickly? And ignored the failing test?
The 'docker' way to do such things would be to use an env file...

https://docs.docker.com/compose/how-tos/environment-variables/set-environment-variables/#use-the-env_file-attribute

[buckaroogeek]

Many thanks for the quick turn around!

[PromoFaux]

... Not sure how I managed to merge it. Put the PR up just as I was going to dinner.... WIll fix the tests, however.

The 'docker' way

What makes you say this?

https://docs.docker.com/engine/swarm/secrets/#:~:text=Secrets%20are%20encrypted%20during%20transit,those%20service%20tasks%20are%20running.

[rdwebdesign]

The linked page says:

Note

Docker secrets are only available to swarm services, not to standalone containers ...

Does it work for stand alone docker installs too?

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I thought we should recommend using --env_file attribute:

• https://docs.docker.com/reference/compose-file/services/#env_file
• https://docs.docker.com/compose/how-tos/environment-variables/set-environment-variables/#use-the-env_file-attribute

[PromoFaux]

Does it work for stand alone docker installs too?

Certainly appears to work - at least it did when I tried it

Besides which, from the top of your second link: :)

Don't use environment variables to pass sensitive information, such as passwords, in to your containers. Use secrets instead.

[buckaroogeek]

I have been running a Pi-Hole (V5) container using Docker Secrets for quite some time. Works well. The Docker host is a Synology NAS.