Move Log Directory + Fix Permissions

[n7studios]

Summary

• Changes the log folder location from the Plugin's log folder to wp-content/kit-logs, ensuring Plugin checksum verification passes (Linear)
• Replaces WP_Filesystem with wp_mkdir_p, file_put_contents and file methods (Linear). This is similar to Use file_get_contents instead of WP_Filesystem for reading local files convertkit-wordpress#516, which was successful in resolving file permission issues.

Testing

• LogTest integration tests added for the ConvertKit_Log class.

Checklist

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• Code meets WordPress Coding Standards for PHP, HTML, CSS and JS
• Security and Sanitization requirements have been followed
• I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)

[noelherrick]

Does the plugin already initialize the log in its own initialization? I'm just wondering if we need to explicitly call the legacy path deletion. Secondly, do we want to move the logs vs. delete them?

[n7studios]

Does the plugin already initialize the log in its own initialization? I'm just wondering if we need to explicitly call the legacy path deletion.

Plugins (except WooCommerce, which uses WooCommerce's logging system) initialize this class for logging, which would trigger the legacy path deletion. I'd prefer to have that logic here than in each individual Plugin.

Secondly, do we want to move the logs vs. delete them?

Deletion is fine. These logs aren't designed to be long term - only when a creator reaches out for support and we request they enable debugging. We improve security by preventing bad actors guessing the log file name due to using wp_hash for the filename, which is based on the WordPress salt key that's set in wp-config.php.

From Kit/convertkit-wordpress#1174 (review)

should we have a method in the libraries for uninstall

Plugin functions typically aren't available on uninstall.php (example), meaning these libraries might not be available, which is why these libraries don't include such a method - otherwise I'd follow how we call legacy path deletion above from the libraries. Therefore, each plugin is responsible for deleting the log files on Plugin uninstallation.

[noelherrick]

Thanks for your responses!