[Bug]: File Provider Module uses username instead of dav_user to authenticate, breaking non-default user backends

[claucambra]

⚠️ Before submitting, please verify the following: ⚠️

• This is a bug, not a question or a configuration issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server and Desktop Client are up to date. See Server Maintenance and Release Schedule and Desktop Releases for supported versions.
• I agree to follow Nextcloud's Code of Conduct

Bug description

It looks like the fileprovider does not use dav_user (i.e. GUID) in the dav urls it is using, but is using username instead, which causes "Principal with name not found" errors in case where ldap auth is being used

Steps to reproduce

Start client

Expected behavior

File Provider domains should authenticate correctly

Which files are affected by this bug

N/A

Operating system

Mac OS

Which version of the operating system you are running.

macOS 14.4

Package

Other

Nextcloud Server version

28

Nextcloud Desktop Client version

3.13.0-fileprovider-rc1

Is this bug present after an update or on a fresh install?

Fresh desktop client install

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

Are you using an external user-backend?

• Default internal user-backend
• LDAP/ Active Directory
• SSO - SAML
• Other

Nextcloud Server logs

No response

Additional info

No response