feature: #1288 Added The Client Session Design Pattern (#2155)

* #1288 Add client session design pattern

* #1288 Add license to files

* Inserted README file for session_state_pattern

* Added real-world example to client-session/README

* #1288 Add server tests

* #1288 Fixed code smells

* #1288 Removed unused getter and setters

* #1288 incorporated feedback

* #1288 Added maven-assembly-plugin

* #1288 Added more description

Co-authored-by: Nakul Nambiar <u7433687@anu.edu.au>
Co-authored-by: Denis <u7281557@anu.edu.au>

client-session/src/test/java/com/iluwatar/client/session/ServerTest.java

@@ -0,0 +1,14 @@
+package com.iluwatar.client.session;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class ServerTest {
+
+  @Test
+  void checkGetSession() {
+    Server server = new Server("localhost", 8080);
+    Session session = server.getSession("Session");
+    assertEquals("Session", session.getClientName());
+  }
+}