mod_http_upload: Fix issuing slots to components or other non-c2s sessions The 'full_jid' property only exists on local c2s sessions. This was not adjusted for in 0a56dc6c61af, so it did not work. Thanks Fren__ for highlighting the issue.

This module blocks configured queries that change server state.

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

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