feat: new ERP Entity Interface

src/QUI/ERP/ErpEntityInterface.php

+<?php
+
+namespace QUI\ERP;
+
+use QUI;
+use QUI\ERP\Accounting\ArticleList;
+use QUI\ERP\Accounting\Calculations;
+use QUI\ERP\Address as ErpAddress;
+use QUI\ERP\User as ErpUser;
+
+interface ErpEntityInterface
+{
+    /**
+     * Get the customer of the erp entity
+     *
+     * @return ErpUser|null The customer of the order, or null if no customer is set
+     */
+    public function getCustomer(): ?ErpUser;
+
+    /**
+     * Get the currency of the erp entity
+     *
+     * @return Currency\Currency
+     */
+    public function getCurrency(): QUI\ERP\Currency\Currency;
+
+    /**
+     * Get the article list of the erp entity
+     *
+     * @return ArticleList
+     */
+    public function getArticles(): ArticleList;
+
+    /**
+     * Get the price calculation object of the erp entity
+     *
+     * @return Calculations
+     */
+    public function getPriceCalculation(): Calculations;
+
+    /**
+     * Get the delivery address of the erp entity
+     *
+     * @return Address|null
+     */
+    public function getDeliveryAddress(): ?ErpAddress;
+
+    /**
+     * Set a customer to the erp entity
+     *
+     * @param array|QUI\ERP\User|QUI\Interfaces\Users\User $User
+     */
+    public function setCustomer($User);
+}