A SASL mechanism registry will allow the server to introspect user documents and sets of SASL mechanisms, and make decisions about them.

With these classes it should be possible to

• Register SASL mechanisms, by name.
• Construct an instance of a client or server Mechanism object, for a specified mechanism name.
• Produce a list of mechanism names supported by a particular User* object.
• Select a prefered mechanism, from a list of mechanism names.

The registry must be accompanied by a suite of C++ unittests.