Fix transaction description for domain entitlements
Summary:
- Fixed the bug
- Refactored code for better performance
- Moved user_email setting to the observer
Test Plan: ./phpunit
Reviewers: #hkccp_developers, vanmeeuwen
Reviewed By: #hkccp_developers, vanmeeuwen
Subscribers: vanmeeuwen, #hkccp_developers
Differential Revision: https://git.kolab.org/D1366