Context

The OSImageStream concept introduced to pools in https://github.com/openshift/api/pull/2555 does not apply to HCP/Hypershift architectures because:

• HCP/Hypershift does not use MachineConfigPool objects
• HCP/Hypershift does not support cluster-scoped objects like OSImageStream generally
• Need to determine how to provide equivalent OS stream override functionality for HCP/Hypershift deployments

Goals

Research and design solutions for HCP/Hypershift support:

• Determine if NodePool API should have a similar field for specifying OS streams
• Define the field structure and semantics for NodePool context
• Assess compatibility with existing NodePool workflows
• Investigate whether a separate, namespace-scoped object is needed
• Define the object structure and relationship to NodePools
• Document HCP/Hypershift architectural constraints

More context on https://github.com/openshift/api/pull/2555#discussion_r2476002858