Rule for @async detection

Signed-off-by: Juan Manuel Leflet Estrada <jleflete@redhat.com>

default/generated/spring-framework/spring-framework-5.x-to-6.0-core-container.yaml

@@ -20,3 +20,24 @@
   links:
   - title: 'Spring 6.0 migration guide'
     url: https://github.com/spring-projects/spring-framework/wiki/Spring-Framework-6.0-Release-Notes#core-container
+
+- ruleID: spring-framework-5.x-to-6.0-core-container-00010
+  category: potential
+  effort: 2
+  labels:
+    - konveyor.io/source=spring5
+    - konveyor.io/target=spring6+
+  when:
+    java.referenced:
+      pattern: org.springframework.scheduling.annotation.Async
+      location: ANNOTATION
+  description: Methods annotated with @Async must return either Future or void
+  message: |
+    Methods annotated with @Async must return either Future or void. This has long been documented but is now also
+    actively checked and enforced, with an exception thrown for any other return type.
+    
+    If your @Async annotated method does not return `Future` or `void`, please change its signature.
+  links:
+    - title: 'Spring 6.0 migration guide'
+      url: https://github.com/spring-projects/spring-framework/wiki/Spring-Framework-6.0-Release-Notes#core-container
+

default/generated/spring-framework/tests/data/core-container/src/main/java/org/konveyor/Main.java

@@ -1,19 +1,31 @@
 package org.konveyor;
 
 import org.konveyor.beans.Bean;
+import org.springframework.beans.BeanInfoFactory;
+import org.springframework.beans.SimpleBeanInfoFactory;
+import org.springframework.scheduling.annotation.Async;
 
 import java.beans.BeanInfo;
 import java.beans.IntrospectionException;
-
-import org.springframework.beans.BeanInfoFactory;
-import org.springframework.beans.SimpleBeanInfoFactory;
+import java.util.concurrent.RunnableFuture;
 
 public class Main {
 
     public static void main(String[] args) throws IntrospectionException {
         BeanInfoFactory factory = new SimpleBeanInfoFactory();
         BeanInfo beanInfo = factory.getBeanInfo(Bean.class);
         System.out.println(beanInfo.getBeanDescriptor());
+
+
+    }
+
+    @Async
+    public RunnableFuture<String> correctAsyncMethod(String param) {
+        return null;
+    }
+
+    @Async
+    public void correctAsyncMethod2(String param) {
     }
 
 }

default/generated/spring-framework/tests/spring-framework-5.x-to-6.0-core-container.test.yaml

@@ -10,3 +10,10 @@ tests:
       mode: "source-only"
     hasIncidents:
       exactly: 2
+- ruleID: spring-framework-5.x-to-6.0-core-container-00010
+  testCases:
+    - name: tc-1
+      analysisParams:
+        mode: "source-only"
+      hasIncidents:
+        exactly: 2