Docs: Updates Docker Secrets usage information

[buckaroogeek]

Docker secrets has a couple of characteristics that may cause baffling errors where configuration looks correct but the pihole container cannot read the secret. The UID and GID of the secret file on the host must be set to the same value used by the pihole process in the container (typically 1000).

Description

Amends the WEBPASSWORD_FILE variable description to provide both Swarm and Compose related links. Directs reader to a docker secrets section in Tips and Tricks.

Adds Tips and Tricks content for docker secrets noting the requirement that the UID for the secrets file must be the same as the pihole process in the container. Otherwise the process will not be able to read the file.

Motivation and Context

Adds useful information that will reduce baffling problems reading a Docker secrets file (WEBPASSWORD_FILE).

How Has This Been Tested?

Tested on my two pihole instances (synology docker host).

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ X] Amend readme with additional content.

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• [ x] I have updated the documentation accordingly.

[yubiuser]

Thanks for your PR.

I would not put so much info in this readme as it's already quite long and most users probably won't use the secret file.
Instead, I'd link to link to the documentation at

https://docs.pi-hole.net/docker/configuration/#ftlconf_webserver_api_password-examples

and add the necessary info (e.g. UID/GID) there.

[buckaroogeek]

Glad to make the changes. I was thinking that the permissions issue was not immediately obvious to me so a note might help clarify this for others.

Perhaps I should close this PR as unneeded and generate replacements?

[yubiuser]

so a note might help clarify this for others

It is, but I think the readme is not the best place for it.

Perhaps I should close this PR as unneeded and generate replacements?

You could modify the PR to link to the documentation and open a PR at https://github.com/pi-hole/docs

[yubiuser]

The original PR content has been moved to the documentation repo and is PRed with pi-hole/docs#1255