class for send messages about update paper

src/main/java/ru/ulstu/paper/service/PaperMessages.java

@@ -0,0 +1,25 @@
+package ru.ulstu.paper.service;
+
+import ru.ulstu.paper.model.Paper;
+import ru.ulstu.paper.model.PaperDto;
+import ru.ulstu.user.model.UserDto;
+import ru.ulstu.user.service.MailService;
+
+import java.util.List;
+
+public class PaperMessages {
+
+    public final MailService mailService;
+
+    public PaperMessages(MailService mailService){
+        this.mailService = mailService;
+    }
+    private void sendMessageAboutStatusChange(Paper.PaperStatus oldStatus, PaperDto paper){
+        List<UserDto> users = paper.getAuthors();
+        for (UserDto user: users) {
+            mailService.sendEmail(user.getEmail(), "Обновление статуса статьи",
+                    "Статус статьи " + paper.getTitle() + " сменился с " + oldStatus.getName()
+                            + " на " + paper.getStatus().getName());
+        }
+    }
+}