feature : allow auto-expansionning PV

[survivant]

I create a cstor with multiple disks from few nodes in raidmode : stripes. I have around 4T of free space.

I see the allow expanding at true.

I created PVC starting at 150Mi. I'm expecting the PV to increase until there are not free space on the cstor.

Look like now the PV will expand to a max of 1gi.

I'll like to have that feature configurable.

We could have

• a threshold like at 80% of used space -> double the PV size (or.. use a factor in the config.. like 0.5 ...)
• a maximum value. Don't expand over 200Gi
• flag : allowAutomaticExpansion : true/false

the goal is to avoid to rely on manual intervention to increase the size by editing the PVC manually. We will still have to monitor the cstor pool used size.