Fix GraphQL WebSocket HandlerMapping bean ordering

Prior to this commit, the GraphQL WebSocket HandlerMapping bean would be
ordered at position "2", before the RouterFunction variant defined by
Spring Framework at position "3".

Since then, the Spring Framework team changed the default order value
for this one at "-1", see spring-projects/spring-framework#30278.
This prevents the WebSocket upgrade, as the request is handled by the
RouterFunction instead of the WebSocket handler.

This commit updates the handlermapping order and introduces a test to
prevent issues in the future.

Fixes gh-37892

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfiguration.java

@@ -195,7 +195,7 @@ public HandlerMapping graphQlWebSocketMapping(GraphQlWebSocketHandler handler, G
 			mapping.setWebSocketUpgradeMatch(true);
 			mapping.setUrlMap(Collections.singletonMap(path,
 					handler.initWebSocketHttpRequestHandler(new DefaultHandshakeHandler())));
-			mapping.setOrder(2); // Ahead of HTTP endpoint ("routerFunctionMapping" bean)
+			mapping.setOrder(-2); // Ahead of HTTP endpoint ("routerFunctionMapping" bean)
 			return mapping;
 		}
 

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/graphql/servlet/GraphQlWebMvcAutoConfigurationTests.java

@@ -45,7 +45,11 @@
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.MvcResult;
 import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+import org.springframework.web.servlet.HandlerMapping;
 import org.springframework.web.servlet.function.RouterFunction;
+import org.springframework.web.servlet.function.support.RouterFunctionMapping;
+import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;
+import org.springframework.web.socket.server.support.WebSocketHandlerMapping;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.asyncDispatch;
@@ -162,8 +166,12 @@ void shouldSupportCors() {
 
 	@Test
 	void shouldConfigureWebSocketBeans() {
-		this.contextRunner.withPropertyValues("spring.graphql.websocket.path=/ws")
-			.run((context) -> assertThat(context).hasSingleBean(GraphQlWebSocketHandler.class));
+		this.contextRunner.withPropertyValues("spring.graphql.websocket.path=/ws").run((context) -> {
+			assertThat(context).hasSingleBean(GraphQlWebSocketHandler.class);
+			assertThat(context.getBeanProvider(HandlerMapping.class).orderedStream().toList()).containsSubsequence(
+					context.getBean(WebSocketHandlerMapping.class), context.getBean(RouterFunctionMapping.class),
+					context.getBean(RequestMappingHandlerMapping.class));
+		});
 	}
 
 	@Test