Add auto-config for reactive OAuth2 Resource Server

Closes gh-13948

spring-boot-samples/spring-boot-sample-reactive-oauth2-resource-server/src/main/java/sample/oauth2/resource/ExampleController.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2012-2018 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package sample.oauth2.resource;
+
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.security.oauth2.jwt.Jwt;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class ExampleController {
+
+	@GetMapping("/")
+	public String index(@AuthenticationPrincipal Jwt jwt) {
+		return String.format("Hello, %s!", jwt.getSubject());
+	}
+
+}

spring-boot-samples/spring-boot-sample-reactive-oauth2-resource-server/src/main/java/sample/oauth2/resource/SampleReactiveOAuth2ResourceServerApplication.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2012-2018 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package sample.oauth2.resource;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class SampleReactiveOAuth2ResourceServerApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(SampleReactiveOAuth2ResourceServerApplication.class);
+	}
+
+}

spring-boot-samples/spring-boot-sample-reactive-oauth2-resource-server/src/main/resources/application.yml

@@ -0,0 +1,8 @@
+spring:
+  security:
+    oauth2:
+      resource:
+        jwt:
+          jwk:
+          # To run the application, replace this with a valid JWK Set URI
+            set-uri: https://example.com/oauth2/default/v1/keys