Cannot create directories on WebDAV external storage when trailing slash is omitted

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• Nextcloud Server is running on 64bit capable CPU, PHP and OS.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

When trying to create a directory in WebDAV external storage I see the following error in the WebDAV server: MKCOL can create a collection only server: , request: "MKCOL /images HTTP/1.1 As discussed at https://trac.nginx.org/nginx/ticket/1966 Nginx requires a trailing slash, this seems to be a requirement in WebDAV. This function https://github.com/nextcloud/server/blob/dda79b583df319a375e9b012a39bb97490034679/lib/private/Files/Utils/PathHelper.php#L52 removes the trailing slash and it is indirectly used in mkdir https://github.com/nextcloud/server/blob/dda79b583df319a375e9b012a39bb97490034679/lib/private/Files/Storage/DAV.php#L190

A complicated workaround for NGINX exists https://www.robpeck.com/2020/06/making-webdav-actually-work-on-nginx/

Steps to reproduce

1. Try to create a new directory on an Nginx webDAV server

Expected behavior

The MKCOL request includes a trailing slash

Installation method

Community Docker image

Operating system

Debian/Ubuntu

PHP engine version

None

Web server

None

Database engine version

None

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

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

NA

List of activated Apps

NA

Nextcloud Signing status

NA

Nextcloud Logs

NA

Additional info

NA

Start with lib/private/Files/Utils/PathHelper.php around line 52 and lib/private/Files/Storage/DAV.php around line 190, tracing how the directory path reaches mkdir. Reproduce creation against an Nginx WebDAV server and verify that the resulting MKCOL request includes a trailing slash without breaking other directory creation cases.