[Bug]: ContactsManager may overwrite registered addressbook through key/id collission

⚠️ 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.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

All currently needed addressbooksare being registered with server's ContactsManager::registerAddressBook. Internally, it stores the loaded addressbooks in an array, indexed by the getKey() returned by the registered addressbook.

Now AddressBookImpl::getKey() – implementation of the DAV app in server – returns digits.

The implementation of ldap_contacts_backend's implementation returns digits, too. For the offset is different (on my setup at least), all seems fine when working with one configured LDAP connection (for contacs). With two, one registered addressbook is overwritten and thus not considered further down in he business logic.

The index should not be determined by an external value alone. Namespacing is by the implementing class should be safe.

Steps to reproduce

1. enable ldap_contacts_backend
2. configure first LDAP backend for this app
3. configure second LDAP backend for this app
4. In the contacts menu search for a user that is provided by the second LDAP server

Expected behavior

Contact is being shown in the results

Installation method

Manual installation

Operating system

No response

PHP engine version

No response

Web server

No response

Database engine version

No response

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

No response

Are you using the Nextcloud Server Encryption module?

No response

What user-backends are you using?

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

Configuration report

No response

List of activated Apps

dav and ldap_contacts_backend are sufficient

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

Start by reading ContactsManager::registerAddressBook and the getKey() implementations in AddressBookImpl and ldap_contacts_backend. Reproduce the issue with two configured LDAP backends, then verify that both addressbooks remain registered and that a user from the second LDAP server appears in contact search.