Added before property to container for ordered containers

[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)
• 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:

• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
• 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".