Add test notification tool (#28334)

* Add test notification tool

* Add frontend styles

* Remove option from admin view

* Refactor create post and add translations

* Fix several CI errors

* Fix API and frontend snapshots

* Refactor trailing and leading icon on buttons

* Add different button states

* i18n-extract

* Fix wrong text

* Add tests

* Fix wrong string

* Fix test

* feat: E2E send test notifications (#28371)

* Refactor send desktop notification

* Address rest of the feedback

* Fix tests

* Add correct link

* Fix test

---------

Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: yasserfaraazkhan <attitude3cena.yf@gmail.com>

server/channels/app/post.go

@@ -242,6 +242,10 @@ func (a *App) CreatePost(c request.CTX, post *model.Post, channel *model.Channel
 		post.AddProp(model.PostPropsFromBot, "true")
 	}
 
+	if flags.ForceNotification {
+		post.AddProp(model.PostPropsForceNotification, model.NewId())
+	}
+
 	if c.Session().IsOAuth {
 		post.AddProp(model.PostPropsFromOAuthApp, "true")
 	}
@@ -2722,3 +2726,34 @@ func (a *App) CleanUpAfterPostDeletion(c request.CTX, post *model.Post, deleteBy
 
 	return nil
 }
+
+func (a *App) SendTestMessage(c request.CTX, userID string) (*model.Post, *model.AppError) {
+	bot, err := a.GetSystemBot(c)
+	if err != nil {
+		return nil, model.NewAppError("SendTestMessage", "app.notifications.send_test_message.errors.no_bot", nil, "", http.StatusInternalServerError).Wrap(err)
+	}
+
+	channel, err := a.GetOrCreateDirectChannel(c, userID, bot.UserId)
+	if err != nil {
+		return nil, model.NewAppError("SendTestMessage", "app.notifications.send_test_message.errors.no_channel", nil, "", http.StatusInternalServerError).Wrap(err)
+	}
+
+	user, err := a.GetUser(userID)
+	if err != nil {
+		return nil, model.NewAppError("SendTestMessage", "app.notifications.send_test_message.errors.no_user", nil, "", http.StatusInternalServerError).Wrap(err)
+	}
+	T := i18n.GetUserTranslations(user.Locale)
+	post := &model.Post{
+		ChannelId: channel.Id,
+		Message:   T("app.notifications.send_test_message.message_body"),
+		Type:      model.PostTypeDefault,
+		UserId:    bot.UserId,
+	}
+
+	post, err = a.CreatePost(c, post, channel, model.CreatePostFlags{ForceNotification: true})
+	if err != nil {
+		return nil, model.NewAppError("SendTestMessage", "app.notifications.send_test_message.errors.create_post", nil, "", http.StatusInternalServerError).Wrap(err)
+	}
+
+	return post, nil
+}