Remove event table, related views and code (#467)

This PR removes the `event` table (Model) and all associated code that
is no longer needed.

## Changes
- Migrated `Event::mapSeverity()` into
`IncidentHistoryRenderer::mapSeverity()`, rewritten as a `match`
expression
- Cleaned up references to the `event` relation in `Incident`,
`IncidentHistory`, and `Objects` models, and in `ObjectHeader`
- Removed event-related entries from `Links.php`, `configuration.php` ,
and `common.less`
- `Daemon`: The `event_id` passed to the Event by `Daemon` was not used
anywhere (no usage in notifications-worker.js), removed.
- `Daemon`: The message is now fetched from `notification_history`, as
it is the same as previous `event->message` in this case.
```sql
## Use this query to test:
SELECT NOT EXISTS (
    SELECT 1 FROM incident_history ih
        INNER JOIN event e ON e.id = ih.event_id
    WHERE ih.type = 'notified' AND ih.message != e.message
) AS messages_are_equal;
```

## The following classes have been deleted:
- `EventController` and `EventsController` — the list views and event
detail are gone entirely
- `LoadMoreObjectList` widget, which was only used in `EventsController`
- `Event` ORM model 
- `EventDetail` and `EventRenderer`

resolves #451

Author: sukhwinder33445

application/controllers/EventController.php

@@ -40,16 +40,6 @@
     ]
 );
 
-$section->add(
-    N_('Events'),
-    [
-        'icon'          => 'history',
-        'description'   => $this->translate('Events'),
-        'url'           => 'notifications/events',
-        'priority'      => 20
-    ]
-);
-
 if ($configLandingPage !== null) {
     $section->add(
         N_('Configuration'),

application/controllers/EventsController.php

@@ -17,16 +17,6 @@ public static function sourceAdd(): Url
         return Url::fromPath('notifications/sources/add');
     }
 
-    public static function event(int $id): Url
-    {
-        return Url::fromPath('notifications/event', ['id' => $id]);
-    }
-
-    public static function events(): Url
-    {
-        return Url::fromPath('notifications/events');
-    }
-
     public static function incidents(): Url
     {
         return Url::fromPath('notifications/incidents');

configuration.php

@@ -252,7 +252,7 @@ protected function processNotifications(): void
 
         // grab new notifications and the current connections
         $notifications = IncidentHistory::on(Database::get())
-            ->with(['event', 'incident', 'incident.object', 'incident.object.source'])
+            ->with(['incident', 'incident.object', 'incident.object.source'])
             ->withColumns(['incident.object.id_tags'])
             ->filter(Filter::greaterThan('id', $this->lastIncidentId))
             ->filter(Filter::equal('type', 'notified'))
@@ -287,10 +287,9 @@ protected function processNotifications(): void
                         $notification->contact_id,
                         (object) [
                             'incident_id' => $notification->incident_id,
-                            'event_id'    => $notification->event_id,
                             'severity'    => $incident->severity,
                             'title'       => ObjectsRendererHook::getObjectNameAsString($incident->object),
-                            'message'     => $notification->event->message
+                            'message'     => $notification->message
                         ]
                     )
                 ]);