Add support for showing the native OS incoming call screen when starting new Element Calls

ElementX/Sources/Services/ElementCall/ElementCallServiceProtocol.swift

@@ -0,0 +1,40 @@
+//
+// Copyright 2024 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 Combine
+
+enum ElementCallServiceAction {
+    case answerCall(roomID: String)
+    case declineCall(roomID: String)
+}
+
+enum ElementCallServiceNotificationKey: String {
+    case roomID
+    case roomDisplayName
+    case senderID
+    case senderDisplayName
+}
+
+let ElementCallServiceNotificationDiscardDelta = 10.0
+
+// sourcery: AutoMockable
+protocol ElementCallServiceProtocol {
+    var actions: AnyPublisher<ElementCallServiceAction, Never> { get }
+    
+    func setupCallSession(title: String) async
+    
+    func tearDownCallSession()
+}