Add interface for bindings that use a relay state

Author: tvdijen

src/Binding/HTTPArtifact.php

@@ -42,7 +42,7 @@
  *
  * @package simplesamlphp/saml2
  */
-class HTTPArtifact extends Binding
+class HTTPArtifact extends Binding implements RelayStateInterface
 {
     use RelayStateTrait;
 

src/Binding/HTTPPost.php

@@ -27,7 +27,7 @@
  *
  * @package simplesamlphp/saml2
  */
-class HTTPPost extends Binding
+class HTTPPost extends Binding implements RelayStateInterface
 {
     use RelayStateTrait;
 

src/Binding/HTTPRedirect.php

@@ -38,7 +38,7 @@
  *
  * @package simplesamlphp/saml2
  */
-class HTTPRedirect extends Binding
+class HTTPRedirect extends Binding implements RelayStateInterface
 {
     use RelayStateTrait;
 

src/Binding/RelayStateInterface.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\SAML2\Binding;
+
+/**
+ * Interface grouping common functionality for binding that use a RelayState.
+ *
+ * @package simplesamlphp/saml2
+ */
+interface RelayStateInterface
+{
+    /**
+     * Set the RelayState associated with he message.
+     *
+     * @param string|null $relayState The RelayState.
+     */
+    public function setRelayState(?string $relayState = null): void;
+
+
+    /**
+     * Get the RelayState associated with the message.
+     *
+     * @return string|null The RelayState.
+     */
+    public function getRelayState(): ?string;
+}