Studio: Ensure wp-config constants are defined after import

[katinthehatsite]

Related issues

Closes https://github.com/Automattic/dotcom-forge/issues/10148

Proposed Changes

This PR adds polyfill for database constants in case they are not defined in the wp-config.php file when it is being imported. This ensures that the database constants are defined when the site is started.

Testing Instructions

• Pull the changes from this branch
• Download a backup from this site: https://mc.a8c.com/rewind/debugger.php?site=138657400
• Navigate to Import/Export tab in Studio
• Drop this backup to import it into a site
• Observe that the import succeeds and the site starts successfully

Alternatively, you can export a Studio site, edit wp-config.php file and remove the constants such as DB_HOST etc. from that file. You can then attempt to import it and confirm that the import succeeds and that the site starts successfully.

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[wojtekn]

@katinthehatsite, what if we simplified it and skipped the wp-config.php import if it's invalid, leaving the default one in place? Or maybe we could have a PHP polyfill that sets each constant if it doesn't exist?

[katinthehatsite]

Or maybe we could have a PHP polyfill that sets each constant if it doesn't exist?

For now I went with this approach so that user's config gets preserved. Happy to change it though if it seems overly complicated.

what if we simplified it and skipped the wp-config.php import if it's invalid, leaving the default one in place?

We can also do that as an alternative. Could there be any data that would be vital in the user's config that we could miss by keeping the default config in place?

[katinthehatsite]

I sort of added this check for the case when the user imports a config and the config might have polyfill added already (if they imported a site into Studio from elsewhere and then exported it again out of Studio and imported it the second time) to avoid adding this twice.

There might be a better approach though, not completely sure on this one.

[katinthehatsite]

what if we simplified it and skipped the wp-config.php import if it's invalid, leaving the default one in place?

The more I think about this, the more I think it is the better approach. I will wait for the clarification on my question and will adjust accordingly.