Add exception handling of asynchronous method

Prior to this commit, an exception thrown by an @Async void method
was not further processed as there is no way to transmit that
exception to the caller.

The AsyncUncaughtExceptionHandler is a new strategy interface that
can be implemented to handle unexpected exception thrown during the
invocation of such asynchronous method.

The handler can be specified using either the XML namespace or by
implementing the AsyncConfigurer interface with the EnableAsync
annotation.

Issue: SPR-8995

src/asciidoc/index.adoc

@@ -44652,6 +44652,28 @@ specified with the `<qualifier>` element or Spring's `@Qualifier` annotation.
 
 
 
+[[scheduling-annotation-support-exception]]
+==== Exception management with @Async
+When an `@Async` method has a `Future` typed return value, it is easy to manage
+an exception that was thrown during the method execution as this exception will
+be thrown when calling `get` on the `Future` result. With a void return type
+however, the exception is uncaught and cannot be transmitted. For those cases, an
+`AsyncUncaughtExceptionHandler` can be provided to handle such exceptions.
+
+[source,java,indent=0]
+[subs="verbatim,quotes"]
+----
+	public class MyAsyncUncaughtExceptionHandler implements AsyncUncaughtExceptionHandler {
+
+    	@Override
+    	public void handleUncaughtException(Throwable ex, Method method, Object... params) {
+			// handle exception
+    	}
+	}
+----
+
+By default, the exception is simply logged. A custom `AsyncUncaughtExceptionHandler` can
+be defined _via_ `AsyncConfigurer` or the `task:annotation-driven` XML element.
 
 [[scheduling-task-namespace]]
 === The Task Namespace