[Bug]: Scope reset to local when changing an additional email address

⚠️ 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 scope of an additional email address is reset on changing it.

Steps to reproduce

1. Add additional email address in user settings
2. set to federated or published
3. reload page
4. change email address

Expected behavior

Scope stays unchanged

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

shipped

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

Reproduce the issue from user settings by adding an additional email, setting its scope to federated or published, reloading, and changing the address. Trace how the email address and scope are persisted; done means changing the address preserves the selected scope and the behavior is covered by a regression test.