Fix Freemius API with existing Basic Auth

functions.php

<?php

add_filter( 'http_request_args', 'freemius_http_request_args_filter', 1, 2 );
add_filter( 'http_request_args', 'freemius_http_request_args_filter', 9999, 2 );

function freemius_http_request_args_filter( $parsed_args, $url ) {
	if ( false === strpos( $url, '://api.freemius.com' ) ) {
		return $parsed_args;
	}

	if ( empty( $parsed_args['headers'] ) ) {
		return $parsed_args;
	}

	foreach ( $parsed_args['headers'] as $key => $value ) {
		if ( 'Authorization' === $key ) {
			$parsed_args['headers']['Authorization2'] = $value;
		} else if ( 'Authorization2' === $key ) {
			$parsed_args['headers']['Authorization'] = $value;
			unset($parsed_args['headers'][$key]);
		}
	}

	return $parsed_args;
}