[Bug]: System address book does not exist after setup

⚠️ 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

The system address book gets created with the second user added to a Nextcloud. It should happen when the initial user is added at setup time.

Steps to reproduce

1. Set up Nextcloud
2. scan oc_addressbooks for the system address book

Expected behavior

I can find the SAB

Installation method

None

Nextcloud Server version

master

Operating system

None

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

No response

List of activated Apps

n/a

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

Start by tracing how the initial user is created during setup and where the system address book is inserted into oc_addressbooks. Compare that path with the second-user path described in the issue, then add a regression test. Done means the system address book exists immediately after setup with the initial user.