doc: Missing documentation for quota management

[rptb1]

Reference / Storage Drivers / ZFS / Quotas says:

By default, LXD uses the quota property when you set up a quota for your storage volume.

But How to manage storage volumes makes no mention of quotas. (It would be nice if the phrase "set up a quota" and all similar phrases were linked, btw.)

A search of the documentation for quota does not reveal anything.

I'm guessing there are secret configuration keywords on containers and storage volumes that controls quotas. We have zfs.use_refquota that says:

Use refquota instead of quota for space

but again this does not link to how to actually use set or manage a "quota for space".

The only clue I've found is in an example:

lxc storage volume unset default data size
Remotes the size/quota of a custom volume "data" in pool "default".

All of the above applies for instances and profiles as well as "storage volumes". For example How to manage instances does not mention quotas.

Please could we have some documentation for size quotas.

Thanks.

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Document: reference/storage_zfs.md

[github-actions]

Heads up @mionaalex - the "Documentation" label was applied to this issue.