Inject Symfony translator contract, not Laravel's

The Laravel changes with v6, and our translator is primarily an
implementation of the Symfony contract.

src/Forum/Content/Index.php

@@ -15,10 +15,10 @@ use Flarum\Frontend\Document;
 use Flarum\Http\UrlGenerator;
 use Flarum\Settings\SettingsRepositoryInterface;
 use Flarum\User\User;
-use Illuminate\Contracts\Translation\Translator;
 use Illuminate\Contracts\View\Factory;
 use Illuminate\Support\Arr;
 use Psr\Http\Message\ServerRequestInterface as Request;
+use Symfony\Component\Translation\TranslatorInterface;
 
 class Index
 {
@@ -42,14 +42,19 @@ class Index
      */
     protected $url;
 
+    /**
+     * @var TranslatorInterface
+     */
+    protected $translator;
+
     /**
      * @param Client $api
      * @param Factory $view
      * @param SettingsRepositoryInterface $settings
      * @param UrlGenerator $url
-     * @param Translator $translator
+     * @param TranslatorInterface $translator
      */
-    public function __construct(Client $api, Factory $view, SettingsRepositoryInterface $settings, UrlGenerator $url, Translator $translator)
+    public function __construct(Client $api, Factory $view, SettingsRepositoryInterface $settings, UrlGenerator $url, TranslatorInterface $translator)
     {
         $this->api = $api;
         $this->view = $view;

src/User/AccountActivationMailer.php

@@ -14,7 +14,7 @@ use Flarum\Mail\Job\SendRawEmailJob;
 use Flarum\Settings\SettingsRepositoryInterface;
 use Flarum\User\Event\Registered;
 use Illuminate\Contracts\Queue\Queue;
-use Illuminate\Contracts\Translation\Translator;
+use Symfony\Component\Translation\TranslatorInterface;
 
 class AccountActivationMailer
 {
@@ -34,7 +34,7 @@ class AccountActivationMailer
     protected $url;
 
     /**
-     * @var Translator
+     * @var TranslatorInterface
      */
     protected $translator;
 
@@ -42,9 +42,9 @@ class AccountActivationMailer
      * @param \Flarum\Settings\SettingsRepositoryInterface $settings
      * @param Queue $queue
      * @param UrlGenerator $url
-     * @param Translator $translator
+     * @param TranslatorInterface $translator
      */
-    public function __construct(SettingsRepositoryInterface $settings, Queue $queue, UrlGenerator $url, Translator $translator)
+    public function __construct(SettingsRepositoryInterface $settings, Queue $queue, UrlGenerator $url, TranslatorInterface $translator)
     {
         $this->settings = $settings;
         $this->queue = $queue;

src/User/Command/RequestPasswordResetHandler.php

@@ -15,10 +15,10 @@ use Flarum\Settings\SettingsRepositoryInterface;
 use Flarum\User\PasswordToken;
 use Flarum\User\UserRepository;
 use Illuminate\Contracts\Queue\Queue;
-use Illuminate\Contracts\Translation\Translator;
 use Illuminate\Contracts\Validation\Factory;
 use Illuminate\Database\Eloquent\ModelNotFoundException;
 use Illuminate\Validation\ValidationException;
+use Symfony\Component\Translation\TranslatorInterface;
 
 class RequestPasswordResetHandler
 {
@@ -43,7 +43,7 @@ class RequestPasswordResetHandler
     protected $url;
 
     /**
-     * @var Translator
+     * @var TranslatorInterface
      */
     protected $translator;
 
@@ -57,7 +57,7 @@ class RequestPasswordResetHandler
      * @param SettingsRepositoryInterface $settings
      * @param Queue $queue
      * @param UrlGenerator $url
-     * @param Translator $translator
+     * @param TranslatorInterface $translator
      * @param Factory $validatorFactory
      */
     public function __construct(
@@ -65,7 +65,7 @@ class RequestPasswordResetHandler
         SettingsRepositoryInterface $settings,
         Queue $queue,
         UrlGenerator $url,
-        Translator $translator,
+        TranslatorInterface $translator,
         Factory $validatorFactory
     ) {
         $this->users = $users;

src/User/EmailConfirmationMailer.php

@@ -14,7 +14,7 @@ use Flarum\Mail\Job\SendRawEmailJob;
 use Flarum\Settings\SettingsRepositoryInterface;
 use Flarum\User\Event\EmailChangeRequested;
 use Illuminate\Contracts\Queue\Queue;
-use Illuminate\Contracts\Translation\Translator;
+use Symfony\Component\Translation\TranslatorInterface;
 
 class EmailConfirmationMailer
 {
@@ -34,11 +34,11 @@ class EmailConfirmationMailer
     protected $url;
 
     /**
-     * @var Translator
+     * @var TranslatorInterface
      */
     protected $translator;
 
-    public function __construct(SettingsRepositoryInterface $settings, Queue $queue, UrlGenerator $url, Translator $translator)
+    public function __construct(SettingsRepositoryInterface $settings, Queue $queue, UrlGenerator $url, TranslatorInterface $translator)
     {
         $this->settings = $settings;
         $this->queue = $queue;