Add instagram background implementation and generalize application for other identity providers

app/serializers/supplier_user_serializer.rb

@@ -1,6 +1,6 @@
 class SupplierUserSerializer < Qwaiter::Serializer
   self.root = :user
-  attributes :email, :facebook_id, :name
+  attributes :email, :provider, :uid, :name, :avatar
 
   def name
     object.supplier_name

app/serializers/user_user_serializer.rb

@@ -1,6 +1,6 @@
 class UserUserSerializer < Qwaiter::Serializer
   self.root = :user
-  attributes :email, :facebook_id, :name
+  attributes :email, :provider, :uid, :name, :avatar
 
   def name
     object.friends_name