Add limitAggregateUsageOnExpansion backend parameter setting #1074
Description
The limitAggregateUsage Trident backend option currently applies to both new PVC creation and PVC expansion. When an aggregate is above this threshold, new PVC creation can still succeed by trying a different aggregate for provisioning. However, when an aggregate is above this threshold and a PVC expansion is requested, it will always fail. Customers need time to rebalance capacity once they hit the limitAggregateUsage threshold, but they may want PVC expansions to be allowed until that has occurred. For this use case, a different threshold for PVC expansion is required, which I am proposing that we call limitAggregateUsageOnExpansion.