Added a delayed loading when opening a room (#3748)

* added a delayed loader

* fixed an issue where the loading was not stopped

* pr suggestions

ElementX/Sources/FlowCoordinators/RoomFlowCoordinator.swift

@@ -229,6 +229,8 @@ class RoomFlowCoordinator: FlowCoordinatorProtocol {
     private func handleRoomRoute(roomID: String, via: [String], presentationAction: PresentationAction? = nil, animated: Bool) async {
         guard roomID == self.roomID else { fatalError("Navigation route doesn't belong to this room flow.") }
         
+        showLoadingIndicator(delay: .milliseconds(250))
+        defer { hideLoadingIndicator() }
         guard let room = await userSession.clientProxy.roomForIdentifier(roomID) else {
             stateMachine.tryEvent(.presentJoinRoomScreen(via: via), userInfo: EventUserInfo(animated: animated))
             return
@@ -1618,6 +1620,21 @@ class RoomFlowCoordinator: FlowCoordinatorProtocol {
         
         flowCoordinator.start()
     }
+    
+    private static let loadingIndicatorID = "\(RoomFlowCoordinator.self)-Loading"
+    
+    private func showLoadingIndicator(delay: Duration? = nil) {
+        userIndicatorController.submitIndicator(.init(id: Self.loadingIndicatorID,
+                                                      type: .modal(progress: .indeterminate,
+                                                                   interactiveDismissDisabled: false,
+                                                                   allowsInteraction: false),
+                                                      title: L10n.commonLoading, persistent: true),
+                                                delay: delay)
+    }
+    
+    private func hideLoadingIndicator() {
+        userIndicatorController.retractIndicatorWithId(Self.loadingIndicatorID)
+    }
 }
 
 private extension RoomFlowCoordinator {