Introduce support for multiple windows on mac and iPad OS

Once the app starts the WindowManager is configured with SwiftUI's environment OpenWindowAction. It can then be used to register coordinators (that provide the toPresentable view) and an optional flow coordinator (as most of the screens are part of a flow, especially rooms).
Once a coordinator is registed, the WindowManager invokes the OpenWindowAction which in turn makes the Application call its newly introduced WindowManagerWindowType WindowGroup's block to instantiate a new visual window rooting that view.

The WindowManager is also responsible for wrapping the presentable in a disappearance block and clean up the coordinator stack.

# Conflicts:
#	ElementX/Sources/Application/AppCoordinator.swift

ElementX/Sources/Application/Application.swift

@@ -12,6 +12,7 @@ import SwiftUI
 struct Application: App {
     @UIApplicationDelegateAdaptor(AppDelegate.self) private var appDelegate
     @Environment(\.openURL) private var openURL
+    @Environment(\.openWindow) private var openWindow
     
     private var appCoordinator: AppCoordinatorProtocol!
 
@@ -39,19 +40,7 @@ struct Application: App {
                         Divider().ignoresSafeArea()
                     }
                 }
-                .environment(\.openURL, OpenURLAction { url in
-                    if appCoordinator.handleDeepLink(url, isExternalURL: false) {
-                        return .handled
-                    }
-                    
-                    if appCoordinator.handlePotentialPhishingAttempt(url: url, openURLAction: { url in
-                        openURL(url, isExternalURL: false)
-                    }) {
-                        return .handled
-                    }
-
-                    return .systemAction
-                })
+                .environment(\.openURL, openURLAction(appCoordinator: appCoordinator, windowType: nil))
                 .onOpenURL { url in
                     openURL(url, isExternalURL: true)
                 }
@@ -62,14 +51,42 @@ struct Application: App {
                 }
                 .task {
                     appCoordinator.start()
+                    appCoordinator.windowManager.configure(with: openWindow)
                 }
         }
+        .handlesExternalEvents(matching: ["*"])
+        
+        // This is invoked in response of the WindowManager receiving a register
+        // coordinator request and invoking the `OpenWindowAction` with which
+        // it's configured in the task above.
+        WindowGroup(for: WindowManagerWindowType.self) { $type in
+            if let type {
+                appCoordinator.windowManager.windowForType(type)
+                    .environment(\.openURL, openURLAction(appCoordinator: appCoordinator, windowType: type))
+            }
+        }
+    }
+    
+    private func openURLAction(appCoordinator: AppCoordinatorProtocol, windowType: WindowManagerWindowType?) -> OpenURLAction {
+        .init { url in
+            if appCoordinator.handleDeepLink(url, isExternalURL: false, windowType: windowType) {
+                return .handled
+            }
+            
+            if appCoordinator.handlePotentialPhishingAttempt(url: url, openURLAction: { url in
+                openURL(url, isExternalURL: false)
+            }) {
+                return .handled
+            }
+            
+            return .systemAction
+        }
     }
     
     // MARK: - Private
     
     private func openURL(_ url: URL, isExternalURL: Bool) {
-        if !appCoordinator.handleDeepLink(url, isExternalURL: isExternalURL) {
+        if !appCoordinator.handleDeepLink(url, isExternalURL: isExternalURL, windowType: nil) {
             openURLInSystemBrowser(url)
         }
     }