Draining can block transparently a scalable resource scale down / delete operation

[enxebre]

What steps did you take and what happened?

Another use case where more signalling in the scalable resource ie. MachineDeployment / MachineSet would be useful is when drain is permanently blocked by e.g. a pdb. Right now there's no way to understand draining is preventing a scaling down / deletion operation from succeeding by looking at the MD/MS status.

May be DrainingSucceededCondition when present could be included in the machine ready summary which would be able up into machineSets via MachinesReadyCondition and so into MachineDeployments via #9262

What did you expect to happen?

As an entity interacting with MD/MS I can understand draining is blocking scale down / deletion

Cluster API version

latest

Kubernetes version

No response

Anything else you would like to add?

No response

Label(s) to be applied

/kind bug
One or more /area label. See https://github.com/kubernetes-sigs/cluster-api/labels?q=area for the list of labels.

[sbueringer]

/triage accepted

[typeid]

/assign

[enxebre]

/triage accepted