fix: resolve container width issues, spa redirects, and appearance settings overwrite. feat: enhance order/sub details and newsletter layout

includes/Core/Notifications/Channels/ChannelInterface.php

@@ -0,0 +1,57 @@
+<?php
+
+/**
+ * Channel Interface
+ * 
+ * Contract for implementing custom notification channels (WhatsApp, SMS, Telegram, etc.)
+ * 
+ * @package WooNooW\Core\Notifications\Channels
+ */
+
+namespace WooNooW\Core\Notifications\Channels;
+
+interface ChannelInterface
+{
+
+    /**
+     * Get channel unique identifier
+     * 
+     * @return string Channel ID (e.g., 'whatsapp', 'sms', 'telegram')
+     */
+    public function get_id();
+
+    /**
+     * Get channel display label
+     * 
+     * @return string Channel label for UI (e.g., 'WhatsApp', 'SMS', 'Telegram')
+     */
+    public function get_label();
+
+    /**
+     * Check if channel is properly configured
+     * 
+     * Example: API keys are set, credentials are valid, etc.
+     * 
+     * @return bool True if channel is ready to send notifications
+     */
+    public function is_configured();
+
+    /**
+     * Send notification through this channel
+     * 
+     * @param string $event_id Event identifier (e.g., 'order_completed', 'newsletter_confirm')
+     * @param string $recipient Recipient type ('customer', 'staff')
+     * @param array $data Notification context data (order, user, custom vars, etc.)
+     * @return bool|array Success status, or array with 'success' and 'message' keys
+     */
+    public function send($event_id, $recipient, $data);
+
+    /**
+     * Get channel configuration fields for admin settings
+     * 
+     * Optional. Returns array of field definitions for settings UI.
+     * 
+     * @return array Field definitions (e.g., API key, sender number, etc.)
+     */
+    public function get_config_fields();
+}