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>

frontend/src/style.css

@@ -133,6 +133,17 @@ button:hover {
   color: var(--main-bg);
 }
 
+button:disabled {
+  cursor: not-allowed;
+  opacity: 0.6;
+}
+
+button:disabled:hover {
+  background-color: var(--accent-font-dark);
+  transform: none;
+  color: #ffffff;
+}
+
 .video-item.table {
   overflow-x: auto;
   -webkit-overflow-scrolling: touch;