Provide guidance on making secret service work

On Debian, docker appears to be configured to use secret service by default. However, this did not work on my machine:

# docker login -u user -p pass
WARNING! Using --password via the CLI is insecure. Use --password-stdin.
** Message: 00:51:34.306: Remote error from secret service: org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.secrets was not provided by any .service files
Error saving credentials: error storing credentials - err: exit status 1, out: `The name org.freedesktop.secrets was not provided by any .service files`

My internet searches for "secret service" yielded freedesktop specifications for it but nothing related to which program I need to have installed to have it, or how to start it.

From my experience, freedesktop bits do not always come with adequate user documentation, but since it is rather non-trivial to figure out how to make docker not try to use the various gnome desktop services (https://github.com/docker/cli/issues/1219), please consider adding some guidance on how to make the default credential store work, including on a headless machine with no X installed.

No file or test is named. Review the project's credential-store guidance and the Debian setup relevant to Docker's secret service, then document the required components and startup steps for graphical and headless machines, including how users can avoid an unusable default store.