Add request_uri in OAuth2ParameterNames

Closes spring-projectsgh-16947

Author: jgrandja

Diff for: oauth2/oauth2-core/src/main/java/org/springframework/security/oauth2/core/endpoint/OAuth2ParameterNames.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -230,6 +230,13 @@ public final class OAuth2ParameterNames {
 	 */
 	public static final String ACTOR_TOKEN_TYPE = "actor_token_type";
 
+	/**
+	 * {@code request_uri} - used in Pushed Authorization Response and Authorization
+	 * Request.
+	 * @since 6.5
+	 */
+	public static final String REQUEST_URI = "request_uri";
+
 	private OAuth2ParameterNames() {
 	}