Add missing files.

Author: SebastianStehle

src/PhenX.EntityFrameworkCore.BulkInsert/Helpers.cs

@@ -0,0 +1,30 @@
+using System.Text;
+
+using PhenX.EntityFrameworkCore.BulkInsert.Metadata;
+
+namespace PhenX.EntityFrameworkCore.BulkInsert;
+
+internal static class Helpers
+{
+    public static StringBuilder AppendJoin<T>(this StringBuilder sb, string separator, IEnumerable<T> items, Action<StringBuilder, T> formatter)
+    {
+        var first = true;
+        foreach (var item in items)
+        {
+            if (!first)
+            {
+                sb.Append(separator);
+            }
+
+            formatter(sb, item);
+            first = false;
+        }
+
+        return sb;
+    }
+
+    public static StringBuilder AppendColumns(this StringBuilder sb, IReadOnlyList<PropertyMetadata> columns)
+    {
+        return sb.AppendJoin(", ", columns.Select(c => c.QuotedColumName));
+    }
+}