USE_FULLEMAIL_FOR_LOGIN does not apply for CalDAV/CardDAV

[eduardomozart]

Describe the issue

Toggling "USE_FULLEMAIL_FOR_LOGIN" in Z-Push does not affect the way that Username is handled to the CalDAV/CardDAV server - it always uses the user specified on "Logon Information" and doesn't seem to exist any way to control it, as can be seen below:

In the image above, it will use eduardomozart user to connect to CardDAV/CalDAV server. It could:

1. Rely on "USE_FULLEMAIL_FOR_LOGIN" to send eduardomozart@domain.tld to the CardDAV/CalDAV server
2. Use eduardomozart or eduardomozart@domain.tld depending on the settings for %u or %l at backend/{caldav,carddav}/config.php files. Please notice that actually those variables affect only how the URL is parsed, not affect the username used for authentication on CalDAV/CardDAV server.
3. Create variables similar to "USE_FULLEMAIL_FOR_LOGIN" specific to CalDAV/CardDAV login.

To Reproduce
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4. See error

Expected behavior
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Desktop (please complete the following information):

• OS: Windows 11 / MS Outlook 365
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
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