* Add trial length parameter to trial initiation endpoint and email
* Add feature flag that pegs trial length to 7 when disabled
* Add optionality to Identity
* Move feature service injection to identity accounts controller
* Added trial initiation user verification endpoint
* Added explanatory comment for why we add artificial delay
* Updated RegistrationStart to Registration reference event
* Ensure that productTier query param is an int
* Added email value to trial initiation email