Add CrossSigningSetupCoordinator that handles cross signing setup navigation flow.

Riot/Modules/CrossSigning/Setup/CrossSigningSetupCoordinatorParameters.swift

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+// 
+// Copyright 2020 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
+
+/// CrossSigningSetupCoordinator input parameters
+@objcMembers
+class CrossSigningSetupCoordinatorParameters: NSObject {
+    
+    /// The Matrix session
+    let session: MXSession
+    
+    /// The presenter used to show authentication screen(s)
+    let presenter: Presentable
+    
+    /// The title to use in the authentication screen if present.
+    let title: String?
+    
+    /// The message to use in the authentication screen if present.
+    let message: String?
+    
+    init(session: MXSession,
+         presenter: Presentable,
+         title: String?,
+         message: String?) {
+        self.session = session
+        self.presenter = presenter
+        self.title = title
+        self.message = message
+        
+        super.init()
+    }
+}