Forward Authorization to global content repo

When using HTTP Basic Auth with the global media feature the requests would fail as the Auth header is missing. This forwards the auth header if found.
Fixes #377

inc/global_content/namespace.php

@@ -396,5 +396,11 @@ function filter_global_content_requests_for_auth( array $parsed_args, string $ur
 		] );
 	}, $_COOKIE, array_keys( $_COOKIE ) );
 
+	// Check for Auth header and forward it, for Basic Auth feature support.
+	if ( ! isset( $parsed_args['headers']['Authorization'] ) && ! empty( $_SERVER['HTTP_AUTHORIZATION'] ) ) {
+		// phpcs:ignore WordPress.Security.ValidatedSanitizedInput.InputNotSanitized
+		$parsed_args['headers']['Authorization'] = wp_unslash( $_SERVER['HTTP_AUTHORIZATION'] );
+	}
+
 	return $parsed_args;
 }