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.

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summary: Workaround for Dialback with some servers that violate RFC 6120
...

This module provides a workaround for servers that do not set the `to`
attribute on stream headers, which is required per [RFC6120]:

> ## 4.7.2. to
> 
> For initial stream headers in both client-to-server and
> server-to-server communication, the initiating entity MUST include the
> 'to' attribute and MUST set its value to a domainpart that the
> initiating entity knows or expects the receiving entity to service.

As a side effect of [this issue](https://prosody.im/issues/issue/285),
Prosody 0.10 will be unable to do [Dialback][xep220] with servers that
don't follow this.

# Known servers affected

* Openfire 3.10.2 (and probably earlier versions)