ADR proposal "Requirements for container registry" (#212)

* Add ADR: Requirements for container registry

This commit adds the document that should select an appropriate container registry
implementation that meets all defined requirements and makes an architectural
decision on what implementation is fully SCS-compliant and recommended by the SCS.

This commit adds the document structure and is focused to the OSS
health check part.

* Add Required and desirable features check

This commit adds list of required and desirable features of container registry as well as table comparison for selected container registries(Harbor, Quay, Dragonfly)

* Apply suggestions from code review

Remove Docker as an orchestration platform.
Split Authentication - required feature to the auth of system identities and auth of users.

* Split authentication table row

Split it between system identities and users.
Related to 9c75ea2.

* Add ADR: Requirements for container registry

This commit adds the conclusion and decision parts of ADR.

* Mention the storage level multi-tenancy

* fixup! Add ADR: Requirements for container registry

* Remove term "SCS compliance" from the ADR

This commit drops occurrences of the term "SCS compliance" from the ADR.
This term should be discussed and standardized (defined) first
by the SCS community.

* Remove already deprecated projects features from the document

This commit removes support of Notary and Chartmuseum from Harbor
features as Harbor announced their deprecation.

* fixup! Add Required and desirable features check

* Update Decisions/scs-XXXX-v1-requirements-for-container-registry.md

* fixup! Add ADR: Requirements for container registry

* Fix links

* Assign number 0212 and move to Standards.

Signed-off-by: Matej Feder <[email protected]>
Signed-off-by: Roman Hros <[email protected]>
Signed-off-by: Matej Feder <[email protected]>
Signed-off-by: Kurt Garloff <[email protected]>
Co-authored-by: Roman Hros <[email protected]>
Co-authored-by: Joshua Mühlfort <[email protected]>
Co-authored-by: Kurt Garloff <[email protected]>