Update the docs about newly created registries and their features

[piontec]

Tasks

Beta Give feedback

1. Copy and paste the architecture from RFC, update it.
2. Describe setup of the public registry: enabled options, authentication modes.
3. Describe setup of the private registry
4. Where is it and what's the name and URL.
5. How to generate access keys.
6. Security: how to distribute private image in case it's rapidly needed

[marians]

Some notes after I worked on the docs:

• Access to Aliyun private images is currently unclear (not documented)
• Unclear whether private images should be accessed from Docker Hub or Quay. It's possible, but I guess it's not desired.
• For ACR credentials (scope map plus token), a naming convention seems to be a must-have. Otherwise it will become impossible to track ownership and clean up.
• For creating ACR image pull secrets, I think that the CLI method is far superior to the GUI method. We should only document that one, especially to enforce a naming convention.

[marians]

We merged our intranet PRs and have these pages updated now:

• https://intranet.giantswarm.io/docs/product/architecture-specs-adrs/specs/registries/
• https://intranet.giantswarm.io/docs/dev-and-releng/container-registry/

[piontec]

done