Fix extensibility issue since RequestMatcherDelegatingAuthorizationMa…

…nager is final and does not expose any public methods other than what is available through AuthorizationManager. Fixes spring-projects#15948

config/src/main/java/org/springframework/security/config/annotation/web/configurers/AuthorizeHttpRequestsConfigurer.java

@@ -170,7 +170,8 @@ private AuthorizationManager<HttpServletRequest> createAuthorizationManager() {
 							+ ". Try completing it with something like requestUrls().<something>.hasRole('USER')");
 			Assert.state(this.mappingCount > 0,
 					"At least one mapping is required (for example, authorizeHttpRequests().anyRequest().authenticated())");
-			RequestMatcherDelegatingAuthorizationManager manager = postProcess(this.managerBuilder.build());
+			AuthorizationManager<HttpServletRequest> manager = postProcess(
+					(AuthorizationManager<HttpServletRequest>) this.managerBuilder.build());
 			return AuthorizeHttpRequestsConfigurer.this.postProcessor.postProcess(manager);
 		}