Feature: Website SDK (#653)

Add SDK functions

Co-authored-by: Sojan <sojan@pepalo.com>

db/migrate/20200331095710_add_identifier_to_contact.rb

@@ -0,0 +1,7 @@
+class AddIdentifierToContact < ActiveRecord::Migration[6.0]
+  def change
+    add_column :contacts, :identifier, :string, index: true, default: nil
+    add_index :contacts, ['identifier', :account_id], unique: true, name: 'uniq_identifier_per_account_contact'
+    add_index :contacts, ['email', :account_id], unique: true, name: 'uniq_email_per_account_contact'
+  end
+end