mod_auth_cyrus: Add empty 'profile' table to SASL handler objects This is for compatibility with Prosody's built-in util.sasl objects. A SASL profile table usually includes methods supported by the backend, which can be used by SASL mechanism handlers to perform operations (such as testing the password). It also optionally contains a 'cb' field with channel binding method handlers. The Cyrus backend doesn't support channel binding, and doesn't have the same concept of auth backend methods (it handles all that internally, and Prosody has no insight or control over it). Thus, we create an empty profile which informs Prosody that the SASL handler does not support any of the auth or channel binding methods. Some features will not work, but they didn't work anyway. This just makes it explicit. This fixes a traceback in mod_sasl2_fast, which expected SASL handlers to always contain a 'profile' field.

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"
modules_disabled = { "s2s" }
```