1. Proposed title of this feature request

Add Support for ControlPlaneMachineSets in UPI Clusters on Day 2 for AWS and OpenStack providers.

2. What is the nature and description of the request?

Would like the ability to create ControlPlaneMachinesSets on day 2(post OCP cluster install). Per docs, https://docs.openshift.com/container-platform/4.14/machine_management/control_plane_machine_management/cpmso-about.html#cpmso-limita[%E2%80%A6]s_cpmso-about, "Clusters that do not have preexisting machines that represent the control plane nodes cannot use a control plane machine set or enable the use of a control plane machine set after installation. Generally, preexisting control plane machines are only present if a cluster was installed using infrastructure provisioned by the installation program".

Would like to remove the above restriction listed in the documentation to allow management of control plane nodes using Machines and ControlPlaneMachineSets in a UPI cluster as a day 2 post installation configuration.

3. Why does the customer need this? (List the business requirements here)

Customer has existing UPI installed clusters and would like the ability leverage ControlPlaneMachineSets for improved system reliability. Customer has many existing clusters installed via UPI, so re-installing all clusters as IPI is not feasible in a large production environment.

4. List any affected packages or components.

MAPI - Machines, ControlPlaneMachineSets