* fix: downcase email when finding
* feat: add `from_email` class
* refactor: use `from_email`
* feat: add rule to disallow find_by email directly
* chore: remove redundant test
Since the previous imlpmentation didn't do a case-insentive search, a new user would be created, and the error would be raised at the DB layer. With the new changes, this test case is redundant
* refactor: use from_email
