mod_rest: Set type on temp session to satisfy certain auth checks E.g. mod_external_services and some others use `origin.type == "c2s"` as access check, which rejected the previous nil value.

This module blocks configured queries that change server state.

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

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