Make RoleStore protected virtual (#38061)

Author: HaoK

src/Identity/EntityFrameworkCore/src/PublicAPI.Unshipped.txt

@@ -1 +1,2 @@
 #nullable enable
+~virtual Microsoft.AspNetCore.Identity.EntityFrameworkCore.RoleStore<TRole, TContext, TKey, TUserRole, TRoleClaim>.SaveChanges(System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task

src/Identity/EntityFrameworkCore/src/RoleStore.cs

@@ -121,7 +121,7 @@ public RoleStore(TContext context, IdentityErrorDescriber describer = null)
         /// <summary>Saves the current store.</summary>
         /// <param name="cancellationToken">The <see cref="CancellationToken"/> used to propagate notifications that the operation should be canceled.</param>
         /// <returns>The <see cref="Task"/> that represents the asynchronous operation.</returns>
-        private async Task SaveChanges(CancellationToken cancellationToken)
+        protected virtual async Task SaveChanges(CancellationToken cancellationToken)
         {
             if (AutoSaveChanges)
             {