@Override
    public boolean supports(final Credential credential) {
        return credential != null && SpnegoCredential.class.equals(credential.getClass());
    }
Implementation of a CredentialToPrincipalResolver that takes a
SpnegoCredential and returns a SimplePrincipal.

@author Arnaud Lesueur
@author Marc-Antoine Garrigue
@since 3.1
support/cas-server-support-spnego/src/main/java/org/apereo/cas/support/spnego/authentication/principal/SpnegoPrincipalResolver.java