Add settings page check to add_meta_boxes

[foloed]

We had an issue where add_settings_meta_boxes is being called on every edit page on the website.

This resulted in slow queries due to our massive user meta table on pages this shouldn't be called on.

Modified the add_meta_boxes action to accept the post_type argument, and checks against the classes settings_page_id.

[froger-me]

Hi, Thanks for the pull request. Please correct the code to respect WordPress coding standards and the rest of the format everywhere in the code base.

public function add_settings_meta_boxes( $post_type ) {

        if ( $post_type !== self::$settings_page_id ) {

            return;
        }

• spaces in parenthesis around args (WP standards)
• line return before return statement (as the rest of the code base)

I will merge whenever I have time. Looking at how many messages I receive regarding updates, I hope you can see I currently don't have the bandwidth to give any timeline as to when it will be added to the official WP repo. However, I am grateful for the contribution and would like to address it ASAP.

[froger-me]

Manually merged offline to avoid back-and-forth with formatting (1 space missing after if statement and before parenthesis)