Site Editor: Use temporary redirects for deprecated URLs. (#68971)

Modifies the redirects from deprecated site-editor URLs to use 302 temporary redirects rather than 301 permanent redirects. This prevents the browser from caching the redirect as the destination will differ for logged in and logged out users.

This also switches from using `wp_redirect()` to `wp_safe_redirect()` in accordance with best practices when redirecting within a WordPress site.

Follow up to #67199
Incorporating changes in WordPress/wordpress-develop#7903
See https://core.trac.wordpress.org/ticket/62585

Co-authored-by: peterwilsoncc <[email protected]>
Co-authored-by: Mamaduka <[email protected]>

Author: peterwilsoncc

backport-changelog/6.8/7903.md

@@ -1,3 +1,5 @@
 https://github.com/WordPress/wordpress-develop/pull/7903
 
 * https://github.com/WordPress/gutenberg/pull/67199
+* https://github.com/WordPress/gutenberg/pull/68971
+

lib/compat/wordpress-6.8/site-editor.php

@@ -15,6 +15,16 @@ function ( $settings ) {
 	}
 );
 
+/**
+ * Maps old site editor urls to the new updated ones.
+ *
+ * @since 6.8.0
+ * @access private
+ *
+ * @global string $pagenow The filename of the current screen.
+ *
+ * @return string|false The new URL to redirect to, or false if no redirection is needed.
+ */
 function gutenberg_get_site_editor_redirection() {
 	global $pagenow;
 	if ( 'site-editor.php' !== $pagenow || isset( $_REQUEST['p'] ) || ! $_SERVER['QUERY_STRING'] ) {
@@ -96,10 +106,13 @@ function gutenberg_get_site_editor_redirection() {
 	return add_query_arg( array( 'p' => '/' ) );
 }
 
+/**
+ * Redirect old site editor urls to the new updated ones.
+ */
 function gutenberg_redirect_site_editor_deprecated_urls() {
 	$redirection = gutenberg_get_site_editor_redirection();
 	if ( false !== $redirection ) {
-		wp_redirect( $redirection, 301 );
+		wp_safe_redirect( $redirection );
 		exit;
 	}
 }