Description:
    Generates a settings model.

Examples:
    * Generating a settings model (you don't need to specify the Settings::
      namespace)

        $ rails generate settings_model Notification

        # db/migrate/<timestamp>_create_settings_notifications.rb
        class CreateSettingsNotifications < ActiveRecord::Migration[6.0]
          def self.up
            create_table :settings_notifications do |t|
              t.string :var, null: false
              t.text :value, null: true

              t.timestamps
            end

            add_index :settings_notifications, :var, unique: true
          end

          def self.down
            drop_table :settings_notifications
          end
        end

        # app/models/settings/notification.rb
        module Settings
          class Notification < RailsSettings::Base
            self.table_name = :settings_notifications

            # The configuration is cached, change this if you want to force update
            # the cache, or call Setting::Notification.clear_cache
            cache_prefix { "v1" }

            # Define your settings
            # setting :host, type: :string, default: "http://localhost:3000"
            # setting :default_locale, default: "en", type: :string
          end
        end