[bitnami/wordpress] Add env var to disable XML-RPC

[kimdre]

Description of the change

This PR implements a new environment variable to the (Apache) Wordpress image called WORDPRESS_ENABLE_XML_RPC, that lets you disable/block access to the Wordpress XML-RPC endpoint at xmlrpc.php, as this endpoint is deprecated in favor of the now used Wordpress Rest API and may have security vulnerabilities.
The current best-practice is to disable access to it alltogether if you don't need it, so you should have the abillity to do so in my opinion.

To disable access to the XML-RPC endpoint you can set WORDPRESS_ENABLE_XML_RPC=no.
This will create a new htaccess rule when WordPress is initialized:

# Disable the oudated WordPress XML-RPC endpoint to prevent security vulnerabilities.
<Files xmlrpc.php>
Order Allow,Deny
Deny from all
</Files>

Benefits

By blocking the XML-RPC endpoint you now have one thing less to worry about as a site administrator.
There are also some plugins that do the same, or you could use a filter in the child theme. However, for me, using the htaccess file is the best and safest approach.

Possible drawbacks

Blocking the endpoint could cause problems for users who still use it for access through third-party software.
However, the endpoint has long been deprecated, so further use is already discouraged and it will likely be removed altogether somewhere in the future.

Applicable issues

• fixes [bitnami/wordpress] Add env var to disable XML-RPC  #50755

[carrodher]

Thank you for initiating this pull request. We appreciate your effort. Just a friendly reminder that it's important to sign your commits. Adding your signature certifies that you either authored the patch or have the necessary rights to contribute the changes. You can find detailed information on how to do this in the “Sign your work” section of our contributing guidelines.

Feel free to reach out if you have any questions or need assistance with the signing process.