mod_http_oauth2: Return Authentication Time per OpenID Core Section 2 Mandatory To Implement, either MUST include or OPTIONAL depending on things we don't look at, so might as well include it all the time. Since we do not persist authentication state with cookies or such, the authentication time will always be some point between the user being sent to the authorization endpoint and the time they are sent back to the client application.

Over the years, some servers stop working for various reasons, and leave
behind broken roster subscriptions that trigger failing s2s connections.
This module allows cleaning up such cases by unsubscribing local users
from their contacts on those servers. Also works for typos and the like.
Use with care.

```lua
Component "gmail.com" "unsubscriber"
```