Add buffered data classes

Check it and the concept in background
Use this instead of lines 92-107:
```Java
        // Check whether entry exists
        assertEquals(3, bufferedData.getAcknowledgeIds().getItems().size());
        assertNotNull("No Element found", bufferedData.getAcknowledgeIds().check(item));
        assertEquals(2, bufferedData.getAcknowledgeIds().getItems().size());
        assertNull("Element found, there should be no item", bufferedData.getAcknowledgeIds().check(item));
        assertEquals(2, bufferedData.getAcknowledgeIds().getItems().size());
```