feat(apple): Poll tunnel for new configuration every 1s (#9083)

Similar to how we fetch new resources, we add a Configuration poller
that fetches new configuration every 1s. If the configuration is
unchanged, we respond to the caller with a cached copy to avoid needing
to serialize the data over IPC.

Related: #4505

swift/apple/FirezoneKit/Sources/FirezoneKit/Stores/Store.swift

@@ -14,6 +14,8 @@ import AppKit
 #endif
 
 @MainActor
+// TODO: Move some state logic to view models
+// swiftlint:disable:next type_body_length
 public final class Store: ObservableObject {
   @Published private(set) var favorites = Favorites()
   @Published private(set) var resourceList: ResourceList = .loading
@@ -36,6 +38,8 @@ public final class Store: ObservableObject {
 
   let sessionNotification = SessionNotification()
 
+  private var configurationTimer: Timer?
+  private var configurationUpdateTask: Task<Void, Never>?
   private var resourcesTimer: Timer?
   private var resourceUpdateTask: Task<Void, Never>?
 
@@ -105,6 +109,14 @@ public final class Store: ObservableObject {
   func handleStatusChange(newStatus: NEVPNStatus) async throws {
     status = newStatus
 
+    if status == .invalid {
+      // VPN configuration was yanked from system settings
+      endConfigurationPolling()
+    } else {
+      // This is a no-op if the timer is already active
+      beginConfigurationPolling()
+    }
+
     if status == .connected {
       beginUpdatingResources()
     } else {
@@ -273,6 +285,43 @@ public final class Store: ObservableObject {
     try ipcClient().start(token: token)
   }
 
+  private func beginConfigurationPolling() {
+    // Ensure we're idempotent if called twice
+    if self.configurationTimer != nil {
+      return
+    }
+
+    let updateConfiguration: @Sendable (Timer) -> Void = { _ in
+      Task {
+        await MainActor.run {
+          self.configurationUpdateTask?.cancel()
+          self.configurationUpdateTask = Task {
+            if !Task.isCancelled {
+              do {
+                self.configuration = try await self.ipcClient().getConfiguration()
+              } catch {
+                Log.error(error)
+              }
+            }
+          }
+        }
+      }
+    }
+
+    let intervalInSeconds: TimeInterval = 1
+    let timer = Timer(timeInterval: intervalInSeconds, repeats: true, block: updateConfiguration)
+
+    RunLoop.main.add(timer, forMode: .common)
+    self.configurationTimer = timer
+  }
+
+  private func endConfigurationPolling() {
+    configurationUpdateTask?.cancel()
+    configurationTimer?.invalidate()
+    configurationTimer = nil
+    self.configuration = nil
+  }
+
   // Network Extensions don't have a 2-way binding up to the GUI process,
   // so we need to periodically ask the tunnel process for them.
   private func beginUpdatingResources() {