Add details of the request mapping conditions to mappings endpoint

Closes gh-12080

spring-boot-samples/spring-boot-sample-webflux/src/main/java/sample/webflux/ExampleController.java

@@ -0,0 +1,16 @@
+package sample.webflux;
+
+import org.springframework.http.MediaType;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class ExampleController {
+
+	@PostMapping(path = "/", consumes = { MediaType.APPLICATION_JSON_VALUE,
+			"!application/xml" }, produces = MediaType.TEXT_PLAIN_VALUE, headers = "X-Custom=Foo", params = "a!=alpha")
+	public String example() {
+		return "Hello World";
+	}
+
+}