HTTP method override feature for web-servers that don't allow PUT and DELETE

[gugglegum]

Added HTTP method override feature for web-servers that restrict HTTP method to GET and POST only (don't allow PUT and DELETE)

Some web-servers restrict HTTP methods to only GET and POST. Woo-Commerce uses PUT and DELETE in its API. But there are 2 workarounds for such servers:

1. Use the POST method and add the "_method=" query parameter to the URL using the real HTTP method.
2. Use the POST method and add the "X-HTTP-Method-Override" HTTP header with real HTTP method to the request.

Both variants are equivalent. And they can even be used together. This fork adds possibility to use these workarounds.

More information on this can be found here:

• https://developer.wordpress.org/rest-api/using-the-rest-api/global-parameters/#_method-or-x-http-method-override-header
• https://gridpane.com/kb/put-requests-woocommerce-api/
• https://gridpane.com/kb/making-nginx-accept-put-delete-and-patch-verbs/
• Method override doesnt work with Rest Api. Ex. _method=PUT woocommerce#15218

All you need to do to activate workaround is to add 1 or 2 options to constructor of the Client like in this example:

use Automattic\WooCommerce\Client;

$client = new Client($url, $consumerKey, $consumerSecret, [
    'wp_api' => true,
    'version' => 'wc/v3',
    'follow_redirects' => true,
    'query_string_auth' => true,
    'timeout' => 60,
    'method_override_query' => true,
    'method_override_header' => false,
]);

The options method_override_query activates ?_method=PUT/DELETE workaround. And the option method_override_header activates workaround with X-HTTP-Method-Override header. Usually it's enough to activate only one of them, but you can activate they both if you want.

If you want to better understand how it's working on Woo-Commerce side, you can review the code in the file class-wc-api-server.php. At the moment this code looks like this:

// Compatibility for clients that can't use PUT/PATCH/DELETE
if ( isset( $_GET['_method'] ) ) {
    $this->method = strtoupper( $_GET['_method'] );
} elseif ( isset( $_SERVER['HTTP_X_HTTP_METHOD_OVERRIDE'] ) ) {
    $this->method = $_SERVER['HTTP_X_HTTP_METHOD_OVERRIDE'];
}