* 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
This change allows the user to configure both IMAP and SMTP for an email inbox. IMAP enables the user to see emails in Chatwoot. And user can use SMTP to reply to an email conversation.
Users can use the default settings to send and receive emails for email inboxes if both IMAP and SMTP are disabled.
Fixes#2520
