docs: refactor Authenticating to container registries.

[themr0c]

Is your enhancement related to a problem? Please describe

Current state
3 pages:

1. Registries / Working with container registries
2. Authenticating to a registry / Authenticating to a pre-configured registry
3. Adding an insecure registry / Adding an Insecure Registry to Podman Desktop

Problems:

1. Not indexed by Google: https://podman-desktop.io/docs/containers/registries - Reason: “Crawled - currently not indexed”. Probably because of too sparse content.
2. Most probably useful content is in (2), would be better in (1).
3. Inconsistencies: working / authenticating to / adding?
4. Missing good practice direction: default action vs. advanced / alternate.
5. Missing one story: adding a (secure) custom registry.

Describe the solution you'd like

1. Documentation strategy is following a new direction: aim for learning-oriented tutorials rather than task oriented how-tos.
2. Therefore, define the content structure following the Tutorial guide and Tutorial template from The Good Docs Project.
3. Differentiate clearly between the documentation states:
   1. Define the intent and the outline in a collaboration platform enabling comments and suggestions, such as Gdoc: https://docs.google.com/document/d/1fGXU_DkfN_O80KRZlIAX_38AU2ncRUJBMKDWoGxOkI0/edit.
   2. Draft the content in Markdown native collaboration platform such as HackMd: https://hackmd.io/g96tN9zGRpuPdggYVMLXgg#.
   3. Finalize in a pull request.

New outline that has been accepted:

• Discussed and chosen in https://docs.google.com/document/d/1fGXU_DkfN_O80KRZlIAX_38AU2ncRUJBMKDWoGxOkI0/edit
• Drafted in https://hackmd.io/g96tN9zGRpuPdggYVMLXgg#

1. A single page, with sections:
   10. Overview
   11. Before you start
   12. Setting up a pre-configured container registry
   13. Setting up a custom container registry
   14. Setting up a custom container registry with an insecure certificate
   15. Verifying your registry is properly configured
   16. Changing your registry credentials
   17. Removing a registry
   18. Understanding the registry configuration
   19. Next steps

Describe alternatives you've considered

Rejected proposals:

(Discussed in https://docs.google.com/document/d/1fGXU_DkfN_O80KRZlIAX_38AU2ncRUJBMKDWoGxOkI0/edit)

New outline, proposal 1:

(A) Setting up pre-configured registries
(B) Setting up custom registries <Tabs: Windows, macOS, Linux>
<Optional step: when the registry has an insecure certificate, such as a self-signed certificate>
Outline explanation:
Merge (2) into (1) -> (A): “Setting up pre-configured registries”.
(3) -> (B) “Setting up custom registries”, with the “insecure registries” as optional steps (

)
Keep 2 pages to avoid nested tabs: (B) already has tabs.

New outline, proposal 2:

Reduce into a single page by using optional steps rather than tabs:
(A) Setting up registries: with 2 optional steps

<Optional step: when the registry has an in

Additional context

No response