Provide Mechanism to Conditionally Install Sub-Components

[srueg]

If a components has many sub-components, a way to install them only if the main-component is installed should be available.

Example:
The crossplane component consists of the main crossplane component and the crossplane-aws and crossplane-cloudscale sub-components. If I include the crossplane-cloudscale component in the cloudsclae cloud provider class, I only want it installed if the crossplane main-component is also installed.

Currently we handle this with an if-statement in the main.jsonnet and app.jsonnet files:

if std.member(inv.classes, 'components.crossplane') then {
  '00_stack': cloudscale_stack,
  '10_provider': cloudscale_provider,
  '20_s3_instance_classes': s3.instance_classes,
} else {}

Maybe there's a better way to model these component dependencies and automatically resolve which ones to (not) install.