specific message layer and 
 messaging context.
 
 <p> Callers do not directly operate on authentication modules.
 Instead, they rely on a ClientAuthContext or ServerAuthContext
 to manage the invocation of modules. A caller obtains an instance
 of ClientAuthContext or ServerAuthContext by calling the respective
 <code>getAuthContext</code> method on a <code>ClientAuthConfig</code>
 or <code>ServerAuthConfig</code> object obtained from an 
 AuthConfigProvider.

 <p> The following represents a typical sequen