enable/disable plugins by config option

lib/foodsoft_messages/lib/foodsoft_messages.rb

@@ -3,4 +3,9 @@ require "foodsoft_messages/user_link"
 require "deface"
 
 module FoodsoftMessages
+  # Return whether messages are used or not.
+  # Enabled by default since it used to be part of the foodsoft core.
+  def self.enabled?
+    FoodsoftConfig[:use_messages] != false
+  end
 end

lib/foodsoft_messages/lib/foodsoft_messages/engine.rb

@@ -1,6 +1,7 @@
 module FoodsoftMessages
   class Engine < ::Rails::Engine
     def navigation(primary, context)
+      return unless FoodsoftMessages.enabled?
       return if primary[:foodcoop].nil?
       sub_nav = primary[:foodcoop].sub_navigation
       sub_nav.items <<

lib/foodsoft_messages/lib/foodsoft_messages/user_link.rb

@@ -6,7 +6,7 @@ module FoodsoftMessages
 
         # modify user presentation link to writing a message for the user
         def show_user_link(user=@current_user)
-          if user.nil?
+          if user.nil? or not FoodsoftMessages.enabled?
             show_user user
           else
             link_to show_user(user), new_message_path('message[mail_to]' => user.id),