Login with IMAP backend doesn't keep domain on IMAP login attempts since last upgrade

[nahuelange]

Steps to reproduce

1. Configure IMAP backend

    array (
      'class' => '\\OCA\\UserExternal\\IMAP',
      'arguments' => array (
          0 => 'imap.domaine.org',
          1 => 993,
          2 => 'ssl',
),

2. login as myuser@domaine.org

Expected behaviour

User_backend should use myuser@domaine.org as IMAP login

Actual behaviour

user_backend strip the domain name and attempts to login as "myuser". If I set explicitly stripdomain to false, it tries to login as "myuser@".

Affected Authentication backend

IMAP

Server configuration

User External App version: (see Nextcloud apps page)
4.0

Operating system:
Nextcloud on official docker

Nextcloud version: (see Nextcloud admin page)
34.0.3.2

Updated from an older Nextcloud/ownCloud or fresh install:
Updated from older versions

[nahuelange]

If i try with "myuser@mynextcloud.domain.org" it doesn't strip the domain.
I do not understand where to configure allowed user domain, if it exists somewhere.

[nahuelange]

I debugged this : a native use had the same e-mail adress as a user from user_external.
The method getByEmail returned first the native used so user_external couldn't find it.