Verifying login data can fail for a number of reasons like temporary
connection failure to the IMAP server, Internal problems of the IMAP
server, or actually wrong username / password combination.
This change logs the reason for login failures, helping server admins to
diagnose login problems and better support their users.
Ideally, we would have an option to pass the reason upwards, so the
NextCloud login system can show appropriate errors to users attempting
to login.
Signed-off-by: Bjoern Kahl <mls@bjoern-kahl.de>
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