TypeGroups Localization and refactor

models/AircraftTypeGroup.php

@@ -24,7 +24,9 @@ class AircraftTypeGroup extends Model
   /**
    * @var array Validation rules
    */
-  public $rules = [];
+  public $rules = [
+    'comment' => 'required',
+  ];
 
   public $belongsToMany = [
     'aircraft_types' => 'GermanAirlinesVa\Fleet\Models\AircraftType',

models/aircrafttypegroup/fields.yaml

@@ -1,5 +1,5 @@
 fields:
   comment:
-    label: Comment
+    label: 'germanairlinesva.fleet::lang.aircraft_type_groups.comment'
     span: auto
     type: text