Notification Handler to handle notifications in foreground (#837)

* changed how the notifications are handled

* local notifications can be decrypted and shown!

* Improved the handling for the mock and for the normal messages

* Avatar images are also displayed

* pr ready, commented some code that is not supposed to be releaaed yet, adjusted some tests and added some source code in the targets

* fixing some swiftlint complaints and removed an unused function

* better swiftlint disable

* addressing PR comments

ElementX/Sources/Services/Timeline/TimelineEventProxy.swift

@@ -0,0 +1,52 @@
+//
+// Copyright 2023 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Foundation
+import MatrixRustSDK
+
+protocol TimelineEventProxyProtocol {
+    var type: TimelineEventType? { get }
+
+    var eventID: String { get }
+
+    var senderID: String { get }
+}
+
+final class TimelineEventProxy: TimelineEventProxyProtocol {
+    private let timelineEvent: TimelineEvent
+
+    init(timelineEvent: TimelineEvent) {
+        self.timelineEvent = timelineEvent
+    }
+
+    var eventID: String {
+        timelineEvent.eventId()
+    }
+
+    var senderID: String {
+        timelineEvent.senderId()
+    }
+
+    var type: TimelineEventType? {
+        try? timelineEvent.eventType()
+    }
+}
+
+struct MockTimelineEventProxy: TimelineEventProxyProtocol {
+    let eventID: String
+    let senderID = ""
+    let type: TimelineEventType? = nil
+}