Implemented Exeption and their handling

src/main/java/mops/gruppen2/domain/Exceptions/EventException.java

@@ -0,0 +1,14 @@
+package mops.gruppen2.domain.Exceptions;
+
+public class EventException extends Exception {
+    private String msg;
+
+    public EventException(String msg) {
+        this.msg = msg;
+    }
+
+    @Override
+    public String getMessage() {
+        return msg;
+    }
+}

src/main/java/mops/gruppen2/domain/Exceptions/UserAlreadyExistsException.java

@@ -0,0 +1,7 @@
+package mops.gruppen2.domain.Exceptions;
+
+public class UserAlreadyExistsException extends EventException {
+   public UserAlreadyExistsException(String msg){
+       super(msg);
+    }
+}

src/main/java/mops/gruppen2/domain/Exceptions/UserNotFoundException.java

@@ -0,0 +1,7 @@
+package mops.gruppen2.domain.Exceptions;
+
+public class UserNotFoundException extends EventException{
+    public  UserNotFoundException(String msg){
+        super(msg);
+    }
+}