Introduce support for Azure Scheduled Events

[I324676]

Hi Colleagues,

Recently we had an issue in our Gardener cluster where Azure performed an unplanned live migration on a couple of our VMs, which resulted in increased n/w latencies for almost 15 mins. This caused multiple processes to timeout, thus affecting our customers.

On verifying with the Azure support colleagues, we understand that Scheduled Events are the only way to be notified of any upcoming activities (unplanned), there's no action that can be performed from the Azure Portal. Also, the Scheduled Events APIs can only be invoked from within a VM, and there's no way to reschedule the activity either.

I therefore request the support for Azure Scheduled Events to be added as part of this extension. Gardener could notify the cluster admin regarding any impending activity, preferably over email, so that cluster admins can decide whether they should already drain the Node to prevent disruptions or if it's safe to ignore the alert. Other option is that Gardener could automatically drain the Node and notify the cluster admins that such an action was performed, which could help with RCAs if any.

Regards
Ninad R N