Removed unnecessary override annotations form Account and EventSpot services.
Added commons codec dependency used for HMAC computation.
Added new constructor for Constant Contact in order to receive the client Secrect.
Provided also getter and setter for clientSecret property.
Added validation methods for billing change notification webhook.
Added BillingChangeNotification model.
Added WebHookValidator class.
Added error messages for "no client secret" and "invalid webhook".
No modification. Just properly formatted the code.
Code comment and cleanup.
Removed log.