Code review

This commit fixes some superficial instances of Broken Access Control 
(https://owasp.org/www-project-top-ten/OWASP_Top_Ten_2017/Top_10-2017_A5-Broken_Access_Control).
There may be some more instances of this, as authorization was only done 
after most of the controllers were done (big mistake).

Some refactoring was also performed, where Route Model Binding with DI 
(dependency injection) was used whenever possible, to increase 
testability of the codebase.
Some reused code was also moved to Helper classes as to enforce DRY; 
There may be some lines of code that are still copy-pasted from other 
parts of the codebase for reuse.

Non-breaking refactoring changes were made, but the app as a whole still 
needs full manual testing, and customised responses to HTTP 500 
responses. Some errors are also not handled gracefully and this wasn't 
checked in this commit.

app/Notifications/ApplicationDenied.php

@@ -52,7 +52,7 @@ class ApplicationDenied extends Notification implements ShouldQueue
                     ->line('Your most recent application has been denied.')
                     ->line('Our review team denies applications for several reasons, including poor answers.')
                     ->line('Please review your application and try again in 30 days.')
-                    ->action('Review application', url(route('showUserApp', ['id' => $this->application->id])))
+                    ->action('Review application', url(route('showUserApp', ['application' => $this->application->id])))
                     ->line('Better luck next time!');
     }
 

app/Notifications/NewApplicant.php

@@ -55,7 +55,7 @@ class NewApplicant extends Notification implements ShouldQueue
                     ->subject(config('app.name') . ' - New application')
                     ->line('Someone has just applied for a position. Check it out!')
                     ->line('You are receiving this because you\'re a staff member at ' . config('app.name') . '.')
-                    ->action('View Application', url(route('showUserApp', ['id' => $this->application->id])))
+                    ->action('View Application', url(route('showUserApp', ['application' => $this->application->id])))
                     ->line('Thank you!');
     }
 
@@ -67,7 +67,7 @@ class NewApplicant extends Notification implements ShouldQueue
         $vacancyDetails['name'] = $this->vacancy->vacancyName;
         $vacancyDetails['slots'] = $this->vacancy->vacancyCount;
 
-        $url = route('showUserApp', ['id' => $this->application->id]);
+        $url = route('showUserApp', ['application' => $this->application->id]);
         $applicant = $this->application->user->name;
 
         return (new SlackMessage)

app/Notifications/NewComment.php

@@ -50,7 +50,7 @@ class NewComment extends Notification implements ShouldQueue
                     ->subject(config('app.name') . ' - New comment')
                     ->line('Someone has just posted a new comment on an application you follow.')
                     ->line('You\'re receiving this email because you\'ve voted/commented on this application.')
-                    ->action('Check it out', url(route('showUserApp', ['id' => $this->application->id])))
+                    ->action('Check it out', url(route('showUserApp', ['application' => $this->application->id])))
                     ->line('Thank you!');
     }
 

app/Notifications/NewContact.php

@@ -0,0 +1,78 @@
+<?php
+
+namespace App\Notifications;
+
+use Illuminate\Bus\Queueable;
+use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Notifications\Messages\MailMessage;
+use Illuminate\Notifications\Notification;
+use Illuminate\Support\Collection;
+
+class NewContact extends Notification
+{
+    use Queueable;
+
+    public $message;
+
+    /**
+     * Create a new notification instance.
+     *
+     * @return void
+     */
+    public function __construct(Collection $message)
+    {
+        $this->message = $message;
+    }
+
+    /**
+     * Get the notification's delivery channels.
+     *
+     * @param  mixed  $notifiable
+     * @return array
+     */
+    public function via($notifiable)
+    {
+        return ['mail'];
+    }
+
+    /**
+     * Get the mail representation of the notification.
+     *
+     * @param  mixed  $notifiable
+     * @return \Illuminate\Notifications\Messages\MailMessage
+     */
+    public function toMail($notifiable)
+    {
+        if ($this->message->has([
+          'message',
+          'ip',
+          'email'
+        ]))
+        {
+          return (new MailMessage)
+                      ->line('We\'ve received a new contact form submission in the StaffManagement app center.')
+                      ->line('This is what they sent: ')
+                      ->line('')
+                      ->line($this->message->get('message'))
+                      ->line('')
+                      ->line('This message was received from ' . $this->message->get('ip') . ' and submitted by ' . $this->message->get('email') . '.')
+                      ->action('Sign in', url(route('login')))
+                      ->line('Thank you!');
+        }
+
+        throw new \InvalidArgumentException("Invalid arguments supplied to NewContact!");
+    }
+
+    /**
+     * Get the array representation of the notification.
+     *
+     * @param  mixed  $notifiable
+     * @return array
+     */
+    public function toArray($notifiable)
+    {
+        return [
+            //
+        ];
+    }
+}