Ordered Container Start in Score - `containers.*.before.containers|ready`

[kai-kystverket]

Added a before property to the container schema to allow ordered executions. This would be implemented as example init container in k8s or depends_on in docker compose.

Description

Added two new fields

• container: A reference to another container which should be run before
• status: The status check to decide when to start the container.

What does this PR do?

Implements #104

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] New chore (expected functionality to be implemented)

Checklist:

• [x] My change requires a change to the documentation.
  • [ ] I have updated the documentation accordingly.
• [x] I've signed off with an email address that matches the commit author.

[mathieu-benoit]

@astromechza, like discussed let's review and merge this one as it will unlock a lot of good use cases with "initContainers".

[mathieu-benoit]

Converting back to draft as we want to manually integrate this new version of the spec in the score-go repo and then manually test this new version in score-compose for example. Once this first loop of tests is done, we'll merge/release everyone. It will take some times from here, but we want to avoid breaking change, etc. with existing implementations.

Update: score-go branch/PR now in place: https://github.com/score-spec/score-go/pull/121.