mod_client_management: Add support for revocation of clients (when possible) We decided to keep the unified listing of "clients", which includes both SASL2 clients and OAuth grants, etc. To a user, or someone wanting to manage what can access their account, they are largely equivalent. To accomplish this technically, we add a prefix to the id to state what type it really is.

This module blocks configured queries that change server state.

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

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