Fix for issue dev/#5037: Standalone install in another language

[jaapjansma]

Overview

Fixes an issue in the installer user interface (for standalone) after selecting a different language.

Before

When installing CiviCRM Standalone through the user interface and one selects a different language an fatal error did appear.

After

When installing CiviCRM Standalone through the user interface and one selects a different language the setup continues and CiviCRM is installed in the selected language.

Technical Details

The issue was caused by not propagating the correct cms.root path.

Comments

Good to know is that the installer downloads the translation files after selected the right language. So no need to download those before installing.
After this PR is merged the installation documentation for standalone in a different language needs an update.

See https://lab.civicrm.org/dev/core/-/issues/5037

[civibot]

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[seamuslee001]

@artfulrobot @ufundo does this work for you folks

[artfulrobot]

I found it hard to test this because standalone won't install through the browser until #29352 is merged. But applying this patch together with that patch, I was able to see it working!

One note that I found a bit confusing: here's the process:

1. visit installer page, it's in English
2. select a different language from the drop down. The page immediately reloads. If the language files are installed, the page will be in the selected language, but otherwise it's still in English.
3. Complete install form.
4. Success message is in selected language.
5. If you delete the db and settings file and access the installer again, then at step (2) you'll see the language because it was downloaded in step 3.

[artfulrobot]

Thanks @jaapjansma