Fixed: (Cardigann) Validate definition file and setting fields existence

Towards #2245

src/NzbDrone.Core/Indexers/Definitions/Cardigann/CardigannSettings.cs

@@ -1,11 +1,23 @@
 using System.Collections.Generic;
+using FluentValidation;
 using NzbDrone.Core.Annotations;
 using NzbDrone.Core.Indexers.Settings;
+using NzbDrone.Core.Validation;
 
 namespace NzbDrone.Core.Indexers.Definitions.Cardigann
 {
+    public class CardigannSettingsValidator : NoAuthSettingsValidator<CardigannSettings>
+    {
+        public CardigannSettingsValidator()
+        {
+            RuleFor(c => c.DefinitionFile).NotEmpty();
+        }
+    }
+
     public class CardigannSettings : NoAuthTorrentBaseSettings
     {
+        private static readonly CardigannSettingsValidator Validator = new ();
+
         public CardigannSettings()
         {
             ExtraFieldData = new Dictionary<string, object>();
@@ -15,5 +27,10 @@ namespace NzbDrone.Core.Indexers.Definitions.Cardigann
         public string DefinitionFile { get; set; }
 
         public Dictionary<string, object> ExtraFieldData { get; set; }
+
+        public override NzbDroneValidationResult Validate()
+        {
+            return new NzbDroneValidationResult(Validator.Validate(this));
+        }
     }
 }