Lots of data and model setup

DCGEngine.Database/Interfaces/IDataSeeder.cs

@@ -0,0 +1,8 @@
+using Microsoft.EntityFrameworkCore;
+
+namespace DCGEngine.Database.Interfaces;
+
+public interface IDataSeeder
+{
+    void Seed(ModelBuilder builder);
+}

DCGEngine.Database/Interfaces/ITimeTrackedEntity.cs

@@ -5,7 +5,7 @@ public interface ITimeTrackedEntity
     /// <summary>
     /// The <see cref="DateTime"/> this entity was first added to the database.
     /// </summary>
-    public DateTime? DateCreated { get; set; }
+    public DateTime DateCreated { get; set; }
     
     /// <summary>
     /// The <see cref="DateTime"/> this entity was last updated.