Language of mail doesn't show as intended by the settings. [ch87] (#6619)

* Fixes #5554. Language of mail doesn't show as intended by the settings.

app/Listeners/CheckoutableListener.php

@@ -40,11 +40,18 @@ class CheckoutableListener
          */
         $acceptance = $this->getCheckoutAcceptance($event);       
 
+        if(!$event->checkedOutTo->locale){
+            Notification::locale(Setting::getSettings()->locale)->send(
+                $this->getNotifiables($event), 
+                $this->getCheckoutNotification($event, $acceptance)
+            );
+        } else {
             Notification::send(
                 $this->getNotifiables($event), 
                 $this->getCheckoutNotification($event, $acceptance)
             );
         }
+    }
 
     /**
      * Notify the user about the checked in checkoutable
@@ -60,11 +67,18 @@ class CheckoutableListener
         /**
          * Send the appropriate notification
          */
+        if(!$event->checkedOutTo->locale){
+            Notification::locale(Setting::getSettings()->locale)->send(
+                $this->getNotifiables($event), 
+                $this->getCheckinNotification($event)
+            );
+        } else {
             Notification::send(
                 $this->getNotifiables($event), 
                 $this->getCheckinNotification($event)
             );
         }
+    }      
 
     /**
      * Generates a checkout acceptance

app/Models/User.php

@@ -15,11 +15,12 @@ use Illuminate\Database\Eloquent\SoftDeletes;
 use App\Http\Traits\UniqueUndeletedTrait;
 use Illuminate\Notifications\Notifiable;
 use Laravel\Passport\HasApiTokens;
+use Illuminate\Contracts\Translation\HasLocalePreference;
 use DB;
 
 
 
-class User extends SnipeModel implements AuthenticatableContract, AuthorizableContract, CanResetPasswordContract
+class User extends SnipeModel implements AuthenticatableContract, AuthorizableContract, CanResetPasswordContract, HasLocalePreference
 {
     protected $presenter = 'App\Presenters\UserPresenter';
     use SoftDeletes, ValidatingTrait;
@@ -643,4 +644,8 @@ class User extends SnipeModel implements AuthenticatableContract, AuthorizableCo
     {
         return $query->leftJoin('departments as departments_users', 'users.department_id', '=', 'departments_users.id')->orderBy('departments_users.name', $order);
     }
+
+    public function preferredLocale(){
+        return $this->locale;
+    }
 }

app/Notifications/CheckinLicenseSeatNotification.php

@@ -96,7 +96,6 @@ class CheckinLicenseSeatNotification extends Notification
      */
     public function toMail($notifiable)
     {
-
         return (new MailMessage)->markdown('notifications.markdown.checkin-license',
             [
                 'item'          => $this->item,