* Misc – Add compatibility for WooCommerce High Performance Order Storage (HPOS)

* Update – Security update.

* Fix – “Call to a member function get_meta() on bool” fatal error when creating a WC product programmatically.

* Feature – Manage the Mailchimp newsletter subscription from the “My Account” page.
* Tweak – MailPoet 2 provider has been marked as deprecated.
* Tweak – Added link to get support in the plugin list.
* Tweak – Open the documentation link in a new tab.
* Tweak – Tested compatibility with WP 6.3.
* Dev – Dropped deprecated plugin code on versions 3.x.
* Dev – Dropped `Campaign Monitor` API client.
* Dev – Dropped deprecated filter hook `wc_newsletter_subscription_checkout_content_location`.
* Dev – Dropped deprecated filter hook `woocommerce_newsletter_mailchimp_api_request`.
* Dev – Updated the minimum requirements to WC 3.7, WP 4.9, and PHP 5.6.

* Misc – Add compatibility for WooCommerce High Performance Order Storage (HPOS)
* Fix – Don’t format empty strings as numbers when exporting to CSV
* Fix – Don’t escape non-string values when exporting to CSV
* Fix – Address an issue with loading field mapping from existing formats when adding a custom format
* Fix – Ensure the “exported by” meta boxes are displayed on the order edit page only