* 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
When the platform update API is called with a new user email, Chatwoot will still follow the same behaviour as in the dashboard where the user will have to confirm the new email activation link until the email gets updated on the user record.
In the case of platform APIs, this might not be the ideal behaviour since the original app will already have a flow to update the user emails. Hence we need to confirm the emails without the extra step in this case
fixes: #4510
