Add upgrade script to fix missing Pronamic subscription IDs in WooCommerce subscription meta

[rvdsteege]

This PR aims to resolve issue #11, by adding an upgrade script which adds the pronamic_subscription_id meta to WooCommerce subscriptions not having this meta.

[remcotolsma]

@rvdsteege I reverted pronamic/wp-pay-core@9a75a8d in pronamic/wp-pay-core@3512f88, because we can't use the class QueryActionsScheduler more widely for now, it is a bit of a YAGNI case. I tried to marge this back in 4f1f491, but have not tested this yet. We also spoke about this code:

wp-pronamic-pay-woocommerce/src/Extension.php

Lines 86 to 92 in 4f1f491

	/**
	* On admin initialize we mark the upgrades as executable. This needs to run before
	* the `wp-pay/core` admin init install routine (priority 5).
	*
	* @link https://github.com/wp-pay/core/blob/2.2.0/src/Admin/Install.php#L65
	*/
	add_action( 'admin_init', [ $this, 'admin_init_upgrades_executable' ], 4 );

wp-pronamic-pay-woocommerce/src/Extension.php

Lines 137 to 146 in 4f1f491

	/**
	* Upgrades are only executable when no Restrict Content Pro upgrade is needed.
	*
	* @return void
	*/
	public function admin_init_upgrades_executable() {
	$executable = function_exists( '\wcs_get_subscription' );
	$this->get_upgrades()->set_executable( $executable );
	}

That requires some adjustments?

And this:

wp-pronamic-pay-woocommerce/src/Upgrade420.php

Lines 160 to 164 in 4f1f491

	public function process_action( string $post_id ) : void {
	// Delete action ID post meta.
	$action_id_meta_key = sprintf( 'pronamic_pay_scheduler_%s_action_id', 'woocommerce_upgrade_4_2_0' );
	\delete_post_meta( (int) $post_id, $action_id_meta_key );

Delete action ID should be done afterwards?

[rvdsteege]

That (upgrades executable) requires some adjustments?

Updated in 4a4a689.

Delete action ID should be done afterwards?

Updated in ae4a27f.