fix(example): use relationship attrs

Author: jaredcnance

src/JsonApiDotNetCoreExample/Models/Person.cs

@@ -13,7 +13,10 @@ public class Person : Identifiable, IHasMeta
         [Attr("last-name")]
         public string LastName { get; set; }
 
+        [HasMany("todo-items")]
         public virtual List<TodoItem> TodoItems { get; set; }
+        
+        [HasMany("todo-item-collections")]
         public virtual List<TodoItemCollection> TodoItemCollections { get; set; }
 
         public Dictionary<string, object> GetMeta(IJsonApiContext context)

src/JsonApiDotNetCoreExample/Models/TodoItem.cs

@@ -12,9 +12,12 @@ public class TodoItem : Identifiable
         public long Ordinal { get; set; }
 
         public int? OwnerId { get; set; }
+        public int? CollectionId { get; set; }
+
+        [HasOne("owner")]
         public virtual Person Owner { get; set; }
 
-        public int? CollectionId { get; set; }
+        [HasOne("collection")]
         public virtual TodoItemCollection Collection { get; set; }
     }
 }

src/JsonApiDotNetCoreExample/Models/TodoItemCollection.cs

@@ -5,9 +5,14 @@ namespace JsonApiDotNetCoreExample.Models
 {
     public class TodoItemCollection : Identifiable
     {
+        [Attr("name")]
         public string Name { get; set; }
-        public virtual List<TodoItem> TodoItems { get; set; }
         public int OwnerId { get; set; }
+
+        [HasMany("todo-items")]
+        public virtual List<TodoItem> TodoItems { get; set; }
+
+        [HasOne("owner")]
         public virtual Person Owner { get; set; }
     }
 }