Foreign key for selected character slots.

Content.Server.Database/Migrations/Postgres/20201006223000_SelectedCharacterSlotFk.cs

@@ -0,0 +1,19 @@
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+namespace Content.Server.Database.Migrations.Postgres
+{
+    [DbContext(typeof(PostgresServerDbContext))]
+    [Migration("20201006223000_SelectedCharacterSlotFk")]
+    public class SelectedCharacterSlotFk : Migration
+    {
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.Sql(@"ALTER TABLE preference
+ADD CONSTRAINT ""FK_preference_profile_selected_character_slot_preference_id""
+FOREIGN KEY (selected_character_slot, preference_id)
+REFERENCES profile (slot, preference_id)
+DEFERRABLE INITIALLY DEFERRED;");
+        }
+    }
+}