Existing courses should have leaderboard disabled (and enabled only for new courses)

Author: sayomaki

priv/repo/migrations/20250429081534_add_leaderboard_display_columns.exs

@@ -1,12 +1,26 @@
 defmodule Cadet.Repo.Migrations.AddLeaderboardDisplayColumns do
   use Ecto.Migration
 
-  def change do
+  def up do
     alter table(:courses) do
       add(:enable_overall_leaderboard, :boolean, null: false, default: true)
       add(:enable_contest_leaderboard, :boolean, null: false, default: true)
       add(:top_leaderboard_display, :integer, default: 100)
       add(:top_contest_leaderboard_display, :integer, default: 10)
     end
+
+    execute("""
+      UPDATE courses
+      SET enable_overall_leaderboard = false, enable_contest_leaderboard = false
+    """)
+  end
+
+  def down do
+    alter table(:courses) do
+      remove(:enable_overall_leaderboard)
+      remove(:enable_contest_leaderboard)
+      remove(:top_leaderboard_display)
+      remove(:top_contest_leaderboard_display)
+    end
   end
 end