sing state to authentication
 contexts for processing by authentication mechanisms (modules).
 <p>
 This interface encapsulates a request message object and a response message object for a message exchange. This
 interface may also be used to associate additional context in the form of key/value pairs, with the encapsulated
 messages.
 <p>
 Every implementation of this interface should provide a zero argument constructor, and a constructor which takes a
 single Map argument. Additional constructors may also