Fix auth state AuthnInstant (simplesamlphp#2478)

* Fix persistence for AuthnInstant data

The time of authentication is handled in the field 'AuthnInstant' and should be persisted in the state in case it is needed.

Author: m0ark

src/SimpleSAML/Auth/State.php

@@ -129,7 +129,7 @@ public static function getPersistentAuthData(array $state): array
             'Attributes',
             'Expire',
             'LogoutState',
-            'AuthInstant',
+            'AuthnInstant',
             'RememberMe',
             'saml:sp:NameID',
         ];

tests/src/SimpleSAML/Auth/StateTest.php

@@ -27,7 +27,7 @@ public function testGetPersistentAuthData(): void
             'Attributes' => [],
             'Expire' => 1234,
             'LogoutState' => 'logoutState',
-            'AuthInstant' => 123456,
+            'AuthnInstant' => 123456,
             'RememberMe' => true,
             'saml:sp:NameID' => 'nameID',
         ];