New: Custom Formats

Co-Authored-By: ta264 <ta264@users.noreply.github.com>

src/Readarr.Http/ClientSchema/Field.cs

@@ -1,4 +1,5 @@
 using System.Collections.Generic;
+using NzbDrone.Core.Annotations;
 
 namespace Readarr.Http.ClientSchema
 {

src/Readarr.Http/REST/RestResource.cs

@@ -5,7 +5,7 @@ namespace Readarr.Http.REST
     public abstract class RestResource
     {
         [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
-        public int Id { get; set; }
+        public virtual int Id { get; set; }
 
         [JsonIgnore]
         public virtual string ResourceName => GetType().Name.ToLowerInvariant().Replace("resource", "");