- Refactored NOTIFIER_HOME to notifier_app_dir to match other roles. This shouldn't change anything since you should've only been overriding COMMON_HOME.
- Refactored `NOTIFIER_HOME` and `NOTIFIER_USER` to `notifier_app_dir` and `notifier_user` to match other roles. This shouldn't change anything since users should've only been overriding COMMON_HOME.