Move source code into "Source" folder

Source/DataLayer/Configurations/ContributorConfig.cs

@@ -0,0 +1,22 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace DataLayer.Configurations
+{
+    internal class ContributorConfig : IEntityTypeConfiguration<Contributor>
+    {
+        public void Configure(EntityTypeBuilder<Contributor> entity)
+        {
+            entity.HasKey(c => c.ContributorId);
+            entity.HasIndex(c => c.Name);
+
+            //entity.OwnsOne(b => b.AuthorProperty);
+            // ... in separate table
+
+            entity
+                .Metadata
+                .FindNavigation(nameof(Contributor.BooksLink))
+                .SetPropertyAccessMode(PropertyAccessMode.Field);
+        }
+    }
+}