mod_storage_xmlarchive: Advertise capabilities (none atm) Both 'total' and 'quota' would be prohibitively expensive for the kind of archives this module targets as it would require counting items across the entire archive.

This module blocks configured queries that change server state.

E.g. to make vCard storage read-only:

``` lua
readonly_stores = {
	vcard = { "vcard-temp", "vCard" };
}
```