[Housekeeping] Refactor settings model (#165)

* [WIP] renamed current settings module and tables to have backup suffix

* Created new settings table, schema, and context

* Migrated from old settings module to new one

* Removed settings backup modules

* Added some tests and docs

priv/repo/migrations/20240404174144_create_new_settings.exs

@@ -0,0 +1,29 @@
+defmodule Pinchflat.Repo.Migrations.CreateNewSettings do
+  use Ecto.Migration
+
+  def up do
+    create table(:settings) do
+      add :onboarding, :boolean, default: true, null: false
+      add :pro_enabled, :boolean, default: false, null: false
+      add :yt_dlp_version, :string
+    end
+
+    # Make an initial record because this will be the only one ever inserted
+    execute "INSERT INTO settings (onboarding, pro_enabled, yt_dlp_version) VALUES (true, false, NULL)"
+
+    # Set the value of onboarding to the previous version set in `settings_backup`
+    execute """
+      UPDATE settings
+      SET onboarding = COALESCE((SELECT value = 'true' FROM settings_backup WHERE name = 'onboarding'), true)
+    """
+
+    execute """
+      UPDATE settings
+      SET pro_enabled = COALESCE((SELECT value = 'true' FROM settings_backup WHERE name = 'pro_enabled'), false)
+    """
+  end
+
+  def down do
+    drop table(:settings)
+  end
+end