1. Proposed title of this feature request

Machine API support for Azure Capacity Reservation Groups

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

The customer would like to configure machinesets to allocate instances from pre-existing Capacity Reservation Groups, see Azure docs below

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

This would allow the customer to create a pool of reserved resources which can be shared between clusters of different priorities. Imagine a test and prod cluster where the demands of the prod cluster suddenly grow. The test cluster is scaled down freeing resources and the prod cluster is scaled up with assurances that those resources remain available, not allocated to another Azure customer.

1. List any affected packages or components.

MAPI/CAPI Azure

In this use case, there's no immediate need for install time support to designate reserved capacity group for control plane resources, however we should consider whether that's desirable from a completeness standpoint. We should also consider whether or not this should be added as an attribute for the installconfig compute machinepool or whether altering generated MachineSet manifests is sufficient, this appears to be a relatively new Azure feature which may or may not see wider customer demand. This customer's primary use case is centered around scaling up and down existing clusters, however others may have different uses for this feature.

https://docs.microsoft.com/en-us/azure/virtual-machines/capacity-reservation-associate-vm?tabs=api1%2Capi2%2Capi3

Additional background on the feature for considering additional use cases

https://techcommunity.microsoft.com/t5/azure-compute-blog/guarantee-capacity-access-with-on-demand-capacity-reservations/ba-p/3269202