ChangeEmailSubscriber: fix user parameters: remove enabled = false, set
email = old value (don't save changes)
Email change: add template
Use TwigSwiftMailer
Override FOSUserBundle Routes:
set pattern "/confirm/{token}/{email}" for fos_user_registration_confirm
Override FosUserBundle RegistrationController
Add parameters for mailer
Use a separate handler to confirm the e-mail address:
RegistrationController: add new method confirmEmailAction
Routing: add new route "/confirm_email/{token}/{email}"
sendEmailMessage: use route "fos_user_registration_confirm_email" to generate confirmationUrl