Add subject-id signal constant + enum

Author: tvdijen

src/Constants.php

@@ -36,6 +36,11 @@ class Constants extends \SimpleSAML\XMLSecurity\Constants
      */
     public const ATTR_SUBJECT_ID = 'urn:oasis:names:tc:SAML:attribute:subject-id';
 
+    /**
+     * Subject signal attribute
+     */
+    public const PROFILE_SUBJECT_ID_REQ = 'urn:oasis:names:tc:SAML:profiles:subject-id:req';
+
     /**
      * The URN for the Holder-of-Key Web Browser SSO Profile binding
      */

src/XML/subjectid/SignalEnum.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\SAML2\XML\subjectid;
+
+enum SignalEnum: string
+{
+    /**
+     * The value MUST be one of the following, signaling the corresponding requirement:
+     */
+
+    /**
+     * The relying party requires the standard identifier Attribute defined in Section 3.3.
+     *
+     * - subject-id
+     */
+    case SUBJECT_ID = 'subject-id';
+
+    /**
+     * The relying party requires the pair-wise identifier Attribute defined in Section 3.4.
+     *
+     * - pairwise-id
+     */
+    case PAIRWISE_ID = 'pairwise-id';
+
+    /**
+     * The relying party does not require any subject identifier and is designed to operate without a
+     * specific user identity (e.g., with authorization based on non-identifying data).
+     *
+     * - none
+     */
+    case NONE = 'none';
+
+    /**
+     * The relying party will accept any of the identifier Attributes defined in this profile but requires at least one.
+     *
+     * - any
+     */
+    case ANY = 'any';
+}