Added delegate that handles rich push from another provider (#625)

* Adding delegate to NotificationServiceExtension to handle multiple providers

* Added error handling

---------

Co-authored-by: Jay Kim <jay@nullavenue.com>

notification-extension/ITBNotificationServiceExtension.swift

@@ -4,15 +4,37 @@
 
 import UserNotifications
 
+public protocol ITBNotificationServiceExtensionDelegate {
+    func notificationServiceDidReceive(_ request: UNNotificationRequest, bestAttemptContent: UNMutableNotificationContent, contentHandler: @escaping (UNNotificationContent) -> Void)
+}
+
 @objc open class ITBNotificationServiceExtension: UNNotificationServiceExtension {
     var contentHandler: ((UNNotificationContent) -> Void)?
     var bestAttemptContent: UNMutableNotificationContent?
+    public static var itblNotificationDelegate: ITBNotificationServiceExtensionDelegate?
 
     @objc override open func didReceive(_ request: UNNotificationRequest,
                                         withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void) {
         self.contentHandler = contentHandler
         bestAttemptContent = (request.content.mutableCopy() as? UNMutableNotificationContent)
 
+        if let itblNotificationDelegate = ITBNotificationServiceExtension.itblNotificationDelegate,
+           let bestAttemptContent = bestAttemptContent {
+
+            let result = request.content.userInfo.contains {
+                guard let itbl = $0.key as? String else {
+                    print("Iterable SDK notification service extension: failed to cast JSON key to string")
+                    return false
+                }
+                return itbl == JsonKey.Payload.metadata
+            }
+
+            if !result {
+                itblNotificationDelegate.notificationServiceDidReceive(request, bestAttemptContent: bestAttemptContent, contentHandler: contentHandler)
+                return
+            }
+        }
+
         resolveCategory(from: request.content)
 
         retrieveAttachment(from: request.content)