feat(relationship-attr): add hasMany and hasOne attribute

Author: jaredcnance

src/JsonApiDotNetCore/Models/HasManyAttribute.cs

@@ -0,0 +1,11 @@
+namespace JsonApiDotNetCore.Models
+{
+    public class HasManyAttribute : RelationshipAttribute
+    {
+        public HasManyAttribute(string publicName)
+        : base(publicName)
+        {
+            PublicRelationshipName = publicName;
+        }
+    }
+}

src/JsonApiDotNetCore/Models/HasOneAttribute.cs

@@ -0,0 +1,11 @@
+namespace JsonApiDotNetCore.Models
+{
+    public class HasOneAttribute : RelationshipAttribute
+    {
+        public HasOneAttribute(string publicName)
+        : base(publicName)
+        {
+            PublicRelationshipName = publicName;
+        }
+    }
+}

src/JsonApiDotNetCore/Models/RelationshipAttribute.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace JsonApiDotNetCore.Models
+{
+    public class RelationshipAttribute : Attribute
+    {
+        protected RelationshipAttribute(string publicName)
+        {
+            PublicRelationshipName = publicName;
+        }
+
+        public string PublicRelationshipName { get; set; }
+        public string InternalRelationshipName { get; set; }
+    }
+}