add foodcoop configuration screen

app/controllers/admin/configs_controller.rb

@@ -0,0 +1,39 @@
+class Admin::ConfigsController < Admin::BaseController
+
+  before_action :get_tabs, only: [:show, :list]
+
+  def show
+    @current_tab = @tabs.include?(params[:tab]) ? params[:tab] : @tabs.first
+    @cfg = FoodsoftConfig
+  end
+
+  def list
+    @current_tab = 'list'
+    @cfg = FoodsoftConfig
+    @dfl = FoodsoftConfig.config
+    @keys = FoodsoftConfig.keys.select {|k| FoodsoftConfig.allowed_key?(k)}.sort
+  end
+
+  def update
+    ActiveRecord::Base.transaction do
+      # TODO support nested configuration keys
+      params[:config].each do |key, val|
+        FoodsoftConfig[key] = val
+      end
+    end
+    flash[:notice] = I18n.t('admin.configs.update.notice')
+    redirect_to action: 'show'
+  end
+
+  protected
+
+  # Set configuration tab names as `@tabs`
+  def get_tabs
+    @tabs = %w(foodcoop payment tasks messages layout language others)
+    # allow engines to modify this list
+    engines = Rails::Engine.subclasses.map(&:instance).select { |e| e.respond_to?(:configuration) }
+    engines.each { |e| e.configuration(@tabs, self) }
+    @tabs.uniq!
+  end
+
+end