[Dembo] Add notification mechanism interfaces

internal/app/service/notification/service/notification.go

@@ -0,0 +1,9 @@
+package service
+
+import (
+	"proctor/pkg/notification/event"
+)
+
+type NotificationService interface {
+	Notify(evt event.Event)
+}

pkg/notification/event/event.go

@@ -0,0 +1,11 @@
+package event
+
+type Event interface {
+	Type() string
+	User() UserData
+	Content() map[string]string
+}
+
+type UserData struct {
+	Email string
+}

pkg/notification/observer.go

@@ -0,0 +1,7 @@
+package notification
+
+import "proctor/pkg/notification/event"
+
+type Observer interface {
+	OnNotify(evt event.Event)
+}