Do not add URLs to the wpr_rocket_cache table if Preload is disabled

[viobru]

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Describe the bug
Currently, any URL that is visited by a real user is added to the wpr_rocket_cache table and automatically assigned a “Complete” status even when the Preload is disabled. This causes the DB to grow too large in some cases.

To Reproduce
Steps to reproduce the behavior:

1. Make sure the Preload is disabled
2. Visit some URLs while not logged-in
3. Check the wpr_rocket_cache table in the DB and you'll find those visited URLs added to it with a "Complete" status

Expected behavior
The table itself is not necessary for the caching process to run effectively, so no URLs should be added to it when the Preload is disabled.

Temporary fix - The snippet below will prevent all URLs from being added to the table if the preload is disabled:

// prevents adding URL to the wpr_rocket_cache table if Preload is disabled
function stop_adding_top_preload( array $regexes ) : array {

	$new_regex = $_SERVER['REQUEST_URI'];
	
	$options = get_option('wp_rocket_settings', []);

	//only if preload is disabled
	if( $options['manual_preload'] == 0) {

		// add the currently visited URL to the exclusions array
		$regexes[] = $new_regex;

	}

return $regexes;
}

add_filter( 'rocket_preload_exclude_urls', 'stop_adding_top_preload');

Screenshots
N/A

Additional context
HS ticket: https://secure.helpscout.net/conversation/2405513676/451397/
Slack thread: https://wp-media.slack.com/archives/C08N8J6VC/p1698938940269529

Acceptance Criteria (for WP Media team use only)

1. When preload is disabled, we should not add URLs to the cache table
2. When enabling preload, there should not be any regression with fetching the sitemaps
3. When the preload is enabled, URLs should be added to the table without regression

[Miraeld]

Reproduce the problem

To reproduce the issue, follow the described steps in the issue.

Identify the root cause

The issue is that we are not checking if the manual preload is true or false here:

wp-rocket/inc/Engine/Preload/Subscriber.php

Lines 449 to 457 in 4c024ba

	public function add_preload_excluded_uri( $regexes ): array {
	$preload_excluded_uri = (array) $this->options->get( 'preload_excluded_uri', [] );
	if ( empty( $preload_excluded_uri ) ) {
	return $regexes;
	}
	return array_merge( $regexes, $preload_excluded_uri );
	}

Scope a solution

To solve the issue, we could add this:

$request_uri = filter_var( wp_unslash( $_SERVER['REQUEST_URI'] ), FILTER_SANITIZE_URL );

if( (bool) !get_rocket_option( 'manual_preload', true ) ) {
	// add the currently visited URL to the exclusions array
	$regexes[] = $request_uri;
}

to the mentioned function.

Effort estimation:

S

Is a refactor needed in that part of the codebase?

No