chore(*): Move old solutions into a separate folder

old/2021/06/Model.cs

@@ -0,0 +1,31 @@
+using System;
+using System.Collections.Generic;
+using Microsoft.EntityFrameworkCore;
+
+namespace Day06
+{
+    public class FishContext : DbContext
+    {
+        public DbSet<Fish> Fishes { get; set; }
+
+        public string DbPath { get; }
+
+        public FishContext()
+        {
+            var folder = Environment.SpecialFolder.LocalApplicationData;
+            var path = Environment.GetFolderPath(folder);
+            DbPath = System.IO.Path.Join(path, "fishes.db");
+        }
+
+        // The following configures EF to create a Sqlite database file in the
+        // special "local" folder for your platform.
+        protected override void OnConfiguring(DbContextOptionsBuilder options)
+            => options.UseSqlite($"Data Source={DbPath}");
+    }
+
+    public class Fish
+    {
+        public int FishId { get; set; }
+        public int InternalTimer { get; set; }
+    }
+}