Merge pull request #527 from json-api-dotnet/hotfix/make-resourcediff-external

hotfix: made resourcediffpair external to be able to unit test my hooks

Author: wisepotato

src/JsonApiDotNetCore/Hooks/Execution/AffectedResourceDiff.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
@@ -31,7 +31,7 @@ public  class ResourceDiff<TEntity> : AffectedResources<TEntity>, IAffectedResou
         /// </summary>
         public HashSet<TEntity> DatabaseValues { get => _databaseValues ?? ThrowNoDbValuesError(); }
 
-        internal ResourceDiff(IEnumerable requestEntities,
+        public ResourceDiff(IEnumerable requestEntities,
                           IEnumerable databaseEntities,
                           Dictionary<RelationshipProxy, IEnumerable> relationships) : base(requestEntities, relationships)
         {
@@ -57,7 +57,7 @@ private HashSet<TEntity> ThrowNoDbValuesError()
 
     public class ResourceDiffPair<TEntity> where TEntity : class, IIdentifiable
     {
-        internal ResourceDiffPair(TEntity entity, TEntity databaseValue)
+        public ResourceDiffPair(TEntity entity, TEntity databaseValue)
         {
             Entity = entity;
             DatabaseValue = databaseValue;