feat: Add Service Stub Pattern using Sentiment Analysis example (#3215)

* Add Service Stub Pattern using Sentiment Analysis example

* Fix Checkstyle issues

* Suppress Sonar warning for Random usage in RealSentimentAnalysisServer

service-stub/src/test/java/com/iluwatar/servicestub/AppTest.java

@@ -0,0 +1,11 @@
+package com.iluwatar.servicestub;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
+public class AppTest {
+  @Test
+  void shouldExecuteWithoutException() {
+    assertDoesNotThrow(() -> App.main(new String[] {}));
+  }
+}