MM-14289 & MM-14884 Push notification acknowledge id and include sender name (#10736)

* MM-14289 Add Push notification acknowledge identifier and store tracing logs

* MM-14884 include SenderName property in Push Notifications

* Remove @ sign from channel Name in push notifications

* Fix i18n

* Fix push notification model

* fix TestPostNotificationGetChannelName

* Remove colon from model constant

* Fix Notification Registry tests

* Make postId optional for clear notifications

* Update http status when service is not available

Co-Authored-By: enahum <nahumhbl@gmail.com>

app/notification_test.go

@@ -997,22 +997,22 @@ func TestPostNotificationGetChannelName(t *testing.T) {
 		},
 		"direct channel, unspecified": {
 			channel:  &model.Channel{Type: model.CHANNEL_DIRECT},
-			expected: "@sender",
+			expected: "sender",
 		},
 		"direct channel, username": {
 			channel:    &model.Channel{Type: model.CHANNEL_DIRECT},
 			nameFormat: model.SHOW_USERNAME,
-			expected:   "@sender",
+			expected:   "sender",
 		},
 		"direct channel, full name": {
 			channel:    &model.Channel{Type: model.CHANNEL_DIRECT},
 			nameFormat: model.SHOW_FULLNAME,
-			expected:   "@Sender Sender",
+			expected:   "Sender Sender",
 		},
 		"direct channel, nickname": {
 			channel:    &model.Channel{Type: model.CHANNEL_DIRECT},
 			nameFormat: model.SHOW_NICKNAME_FULLNAME,
-			expected:   "@Sender",
+			expected:   "Sender",
 		},
 		"group channel, unspecified": {
 			channel:  &model.Channel{Type: model.CHANNEL_GROUP},