feat(backfill): WP CLI script to backfill reader_registered, donation_new events

composer.json

@@ -8,7 +8,7 @@
 		"wp-coding-standards/wpcs": "^3.0",
 		"dealerdirect/phpcodesniffer-composer-installer": "*",
 		"phpcompatibility/phpcompatibility-wp": "*",
-		"yoast/phpunit-polyfills": "^1.0",
+		"yoast/phpunit-polyfills": "^2.0",
 		"phpunit/phpunit": "^7.0 || ^9.5"
 	},
 	"autoload": {

includes/class-initializer.php

@@ -42,6 +42,7 @@ public static function init() {
 		Reader_Roles_Filter::init();
 		User_Update_Watcher::init();
 		Distributor_Customizations::init();
+		Data_Backfill::init();
 
 		register_activation_hook( NEWSPACK_NETWORK_PLUGIN_FILE, [ __CLASS__, 'activation_hook' ] );
 	}