Add links plugin

This can be used to link to external services related to the foodcoop.
With the indirect mode it is possible to implement a secure login to other
services. In that case Foodsoft will send a HTTP GET request and redirect
the user to the returned Location header. This allows the generation of
a one-time login URL.
A typical use-case would be that a workgroup, which is responsible for
the email account, does not need to share the login credentials and can
use a link within the Foodsoft instead.

plugins/links/config/locales/de.yml

@@ -0,0 +1,6 @@
+de:
+  links:
+    show:
+      indirect_no_location: Die konfigurierte URL hat keinen Location Header für die Weiterleitung zurück gegeben.
+  navigation:
+    links: Links

plugins/links/config/locales/en.yml

@@ -0,0 +1,6 @@
+en:
+  links:
+    show:
+      indirect_no_location: The configured URL did not return a Location header for redirection.
+  navigation:
+    links: Links

plugins/links/config/routes.rb

@@ -0,0 +1,9 @@
+Rails.application.routes.draw do
+
+  scope '/:foodcoop' do
+
+    resources :links, only: [:show]
+
+  end
+
+end