Add isolated container and dhii modularity deps

lib/packages/Interop/Container/ServiceProviderInterface.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace WooCommerce\PayPalCommerce\Vendor\Interop\Container;
+
+/**
+ * A service provider provides entries to a container.
+ */
+interface ServiceProviderInterface
+{
+    /**
+     * Returns a list of all container entries registered by this service provider.
+     *
+     * - the key is the entry name
+     * - the value is a callable that will return the entry, aka the **factory**
+     *
+     * Factories have the following signature:
+     *        function(\WooCommerce\PayPalCommerce\Vendor\Psr\Container\ContainerInterface $container)
+     *
+     * @return callable[]
+     */
+    public function getFactories();
+
+    /**
+     * Returns a list of all container entries extended by this service provider.
+     *
+     * - the key is the entry name
+     * - the value is a callable that will return the modified entry
+     *
+     * Callables have the following signature:
+     *        function(WooCommerce\PayPalCommerce\Vendor\Psr\Container\ContainerInterface $container, $previous)
+     *     or function(WooCommerce\PayPalCommerce\Vendor\Psr\Container\ContainerInterface $container, $previous = null)
+     *
+     * About factories parameters:
+     *
+     * - the container (instance of `WooCommerce\PayPalCommerce\Vendor\Psr\Container\ContainerInterface`)
+     * - the entry to be extended. If the entry to be extended does not exist and the parameter is nullable, `null` will be passed.
+     *
+     * @return callable[]
+     */
+    public function getExtensions();
+}