fixes #1961 Adding JSONP support

When using cross-domain requests, it is impossible to read the response
data, and process it.
Using JSONP allows a client, from a specific domain (for example
/domain1), to query data in another doamin (/domain2), and analyze it,
using a callback.

Such a request would be followed by "callback=" parameter. For example:
http://foreman-server:3000/statistics?format=json&callback=analyzeStats

And the response would be:
analyzeStats({"statistics":{"mem_totfree":0.0,"arch_count":{},
"env_count":{},"cpu_count":{},"mem_size":0,"swap_size":0,
"model_count":{},"mem_free":0,"swap_free":0,"klass_count":{},
"os_count":{},"mem_totsize":0.0}})

which will call the analyzeStats callback.
Whereas a regular request,
http://foreman-server:3000/statistics?format=json, will just contain the
JSON data.

More reading on JSONP:
JSONP - http://en.wikipedia.org/wiki/JSONP
JSONP Ruby impl -
www.simb.net/2012/02/06/ruby-and-jsonp
https://github.com/crohr/rack-jsonp/

Gemfile

@@ -1,3 +1,4 @@
+require 'config/settings'
 source 'http://rubygems.org'
 
 gem 'rails', '3.0.17'

bundler.d/jsonp.rb

@@ -0,0 +1,3 @@
+group :jsonp do
+  gem 'rack-jsonp', :require => 'rack/jsonp'
+end if SETTINGS[:support_jsonp]

config/application.rb

@@ -14,6 +14,8 @@
 require File.expand_path('../../lib/timed_cached_store.rb', __FILE__)
 require File.expand_path('../../lib/core_extensions', __FILE__)
 
+Bundler.require(:jsonp) if SETTINGS[:support_jsonp]
+
 module Foreman
   class Application < Rails::Application
     # Setup additional routes by loading all routes file from routes directory
@@ -66,6 +68,9 @@ class Application < Rails::Application
     # enables in memory cache store with ttl
     #config.cache_store = TimedCachedStore.new
     config.cache_store = :file_store, Rails.root.join("tmp")
+
+    # enables JSONP support in the Rack middleware
+    config.middleware.use Rack::JSONP if SETTINGS[:support_jsonp]
   end
 
   def self.setup_console

config/boot.rb

@@ -1,11 +1,6 @@
 require 'rubygems'
 require 'yaml'
-
-root     = File.expand_path(File.dirname(__FILE__) + "/..")
-SETTINGS = YAML.load_file("#{root}/config/settings.yaml")
-SETTINGS[:version]    = File.read(root + "/VERSION").chomp rescue ("N/A")
-SETTINGS[:unattended] = SETTINGS[:unattended].nil? || SETTINGS[:unattended]
-SETTINGS[:login]    ||= SETTINGS[:ldap]
+require 'config/settings'
 
 ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__)
 

config/settings.rb

@@ -0,0 +1,5 @@
+root     = File.expand_path(File.dirname(__FILE__) + "/..")
+SETTINGS = YAML.load_file("#{root}/config/settings.yaml")
+SETTINGS[:version]    = File.read(root + "/VERSION").chomp rescue ("N/A")
+SETTINGS[:unattended] = SETTINGS[:unattended].nil? || SETTINGS[:unattended]
+SETTINGS[:login]    ||= SETTINGS[:ldap]

config/settings.yaml.example

@@ -2,3 +2,6 @@
 :unattended: true
 :login: false
 :require_ssl: false
+#JSONP or "JSON with padding" is a complement to the base JSON data format.
+#It provides a method to request JSON data from a server in a different domain.
+:support_jsonp: false