Add test notification button (#996)

* Add api to test notifications before you save

* Add button to UI

* Inspect apprise logs to get errors

* Better formatting around errors coming back from the test notification endpoint

* Use apprise's built in log capture

* Instruct the user to get error from container log instead of intercepting and parsing apprise logs

* refac move to test method on notification class

---------

Co-authored-by: Simon <simobilleter@gmail.com>

backend/task/urls.py

@@ -34,4 +34,9 @@ urlpatterns = [
         views.ScheduleNotification.as_view(),
         name="api-schedule-notification",
     ),
+    path(
+        "notification/test/",
+        views.NotificationTestView.as_view(),
+        name="api-schedule-notification-test",
+    ),
 ]