mod_http_oauth2: Record details of OAuth client a token is issued to To enable use cases such as revoking all tokens issued to a particular OAuth client in case of security issues, or for informative purposes such as when listing tokens for users.

This module blocks configured queries that change server state.

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

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