feat: implement dummy functions

gemeinsamforschen/src/main/java/unipotsdam/gf/core/management/user/UserService.java

@@ -44,7 +44,7 @@ public class UserService {
             return registrationError();
         }
     }
-    
+
     /**
      * checks if a user exists in order to log him in
      *

gemeinsamforschen/src/main/java/unipotsdam/gf/modules/communication/service/CommunicationDummyService.java

@@ -6,38 +6,46 @@ import unipotsdam.gf.modules.communication.model.Message;
 import unipotsdam.gf.modules.communication.model.chat.ChatMessage;
 import unipotsdam.gf.modules.communication.model.chat.ChatRoom;
 
+import java.time.Instant;
+import java.util.ArrayList;
 import java.util.List;
 
 public class CommunicationDummyService implements ICommunication {
 
     @Override
     public List<ChatMessage> getChatHistory(String roomId) {
-        return null;
+        ArrayList<ChatMessage> chatMessages = new ArrayList<>();
+        int maxValue = 6;
+        for (int i = 1;i <= maxValue;i++) {
+            chatMessages.add(new ChatMessage(String.valueOf(i+1), "Dies ist ein Test" + i + " .",
+                    Instant.now().minusSeconds(maxValue * 10 - i * 10),"testUser" + i));
+        }
+        return chatMessages;
     }
 
     @Override
     public boolean sendMessageToChat(Message message) {
-        return false;
+        throw new RuntimeException("Do not call this method without implementation");
     }
 
     @Override
     public String createChatRoom(String name, List<User> studentIdentifierList) {
-        return null;
+        return "1";
     }
 
     @Override
     public boolean addUserToChatRoom(String roomId, User user) {
-        return false;
+        throw new RuntimeException("Do not call this method without implementation");
     }
 
     @Override
     public boolean setChatRoomTopic(String roomId, String topic) {
-        return false;
+        throw new RuntimeException("Do not call this method without implementation");
     }
 
     @Override
     public ChatRoom getChatRoomInfo(String roomId) {
-        return null;
+        return new ChatRoom("1", "test");
     }
 
     @Override