Website: WP Cloud: Relay secrets for error logger (#1337)

## What is this PR doing?
This PR updates our WP Cloud hosting setup to provide secrets necessary
for error logging to WP.org Slack.

## Testing Instructions

I tested manually playground-dot-wordpress-dot-net.atomicsites.blog via
dev tools console, since the Playground error dialog is hardcoded to log
to playground.wordpress.net.
```
fd = new FormData;
fd.append('description', 'PLEASE IGNORE: This is a test.');
fd.append('logs', 'test-logs');
fd.append('url', 'https://playground-dot-wordpress-dot-net.atomicsites.blog/');
fd.append('context', 'test-context');
fd.append('blueprint', 'test-blueprint');

fetch( '/logger.php', { method: 'POST', body: fd } ).then(r => (console.log('logging response', r), r.text())).then( t => console.log('text', t) )

// Results:
Promise {<pending>}
logging response Response {type: 'basic', url: 'https://playground-dot-wordpress-dot-net.atomicsites.blog/logger.php', redirected: false, status: 200, ok: true, …}
text {"ok":true}
```
And a message was logged to WP.org Slack here:
https://wordpress.slack.com/archives/C06Q5DCKZ3L/p1714150218128469

packages/playground/website-deployment/custom-redirects-lib.php

@@ -9,7 +9,8 @@ function playground_file_needs_special_treatment( $path ) {
 	return (
 		!! playground_maybe_rewrite( $path ) ||
 		!! playground_maybe_redirect( $path ) ||
-		!! playground_get_custom_response_headers( $path )
+		!! playground_get_custom_response_headers( basename( $path ) ) ||
+		!! playground_maybe_set_environment( $path )
 	);
 }
 
@@ -127,12 +128,7 @@ function playground_handle_request() {
 
 	if ( 'php' === $extension ) {
 		$log( "Running PHP: '$resolved_path'" );
-		// TODO: Set these from persistent data for logger.php
-		/*
-		# Slack All
-		SetEnv SLACK_CHANNEL --secret--
-		SetEnv SLACK_TOKEN --secret--
-		*/
+		playground_maybe_set_environment( $requested_path );
 		require $resolved_path;
 	} else {
 		$log( "Reading static file: '$resolved_path'" );
@@ -177,6 +173,32 @@ function playground_maybe_redirect( $requested_path ) {
 	return false;
 }
 
+function playground_maybe_set_environment( $requested_path ) {
+	if ( ! str_ends_with( $requested_path, '.php' ) ) {
+		return false;
+	}
+
+	if ( str_ends_with( $requested_path, 'logger.php' ) ) {
+		// WORKAROUND: Atomic_Persistent_Data wants the DB_PASSWORD constant
+		// which is not set yet. But we can force its definition.
+		__atomic_env_define( 'DB_PASSWORD' );
+
+		$secrets = new Atomic_Persistent_Data;
+		if ( isset(
+			$secrets->LOGGER_SLACK_CHANNEL,
+			$secrets->LOGGER_SLACK_TOKEN,
+		) ) {
+			putenv( "SLACK_CHANNEL={$secrets->LOGGER_SLACK_CHANNEL}" );
+			putenv( "SLACK_TOKEN={$secrets->LOGGER_SLACK_TOKEN}" );
+		} else {
+			error_log( 'PLAYGROUND: Missing secrets for logger.php' );
+		}
+		return true;
+	}
+
+	return false;
+}
+
 function playground_get_custom_response_headers( $filename ) {
 	if ( 'iframe-worker.html' === $filename ) {
 		return array( 'Origin-Agent-Cluster: ?1' );