I'm trying to get notified when userDidAcceptCloudKitShareWith gets called.  Traditionally this was called in the App Delegate but since I am building an iOS 14+ using App as my root object.  I couldn't find any documentation out yet as far as how to add userDidAcceptCloudKitShareWith to my App class, so I am using UIApplicationDelegateAdaptor to use an App Delegate class, however it doesn't seem like userDidAcceptCloudKitShareWith is ever getting called?
import SwiftUI
import CloudKit
// Our observable object class
class ShareDataStore: ObservableObject {
    
    static let shared = ShareDataStore() 
    @Published var didRecieveShare = false
    @Published var shareInfo = ""
}
@main
struct SocialTestAppApp: App {
    
    
    @StateObject var shareDataStore = ShareDataStore.shared 
    
    
    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate
    
    var body: some Scene {
        WindowGroup {
            ContentView().environmentObject(shareDataStore)
        }
    }
}
class AppDelegate: NSObject, UIApplicationDelegate {
    
    let container = CKContainer(identifier: "iCloud.com.TestApp")
    
    
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -> Bool {
        print("did finish launching called")
        return true
    }
    
    
    func application(_ application: UIApplication, userDidAcceptCloudKitShareWith cloudKitShareMetadata: CKShare.Metadata) {
        print("delegate callback called!! ")
        acceptShare(metadata: cloudKitShareMetadata) { result in
            switch result {
            case .success(let recordID):
                print("successful share!")
                ShareDataStore.shared.didRecieveShare = true
                ShareDataStore.shared.shareInfo = recordID.recordName
            case .failure(let error):
                print("failure in share = \(error)")
            }
        }    }
    
    func acceptShare(metadata: CKShare.Metadata,
                     completion: @escaping (Result<CKRecord.ID, Error>) -> Void) {
        
        // Create a reference to the share's container so the operation
        // executes in the correct context.
        let container = CKContainer(identifier: metadata.containerIdentifier)
        
        // Create the operation using the metadata the caller provides.
        let operation = CKAcceptSharesOperation(shareMetadatas: [metadata])
        
        var rootRecordID: CKRecord.ID!
        // If CloudKit accepts the share, cache the root record's ID.
        // The completion closure handles any errors.
        operation.perShareCompletionBlock = { metadata, share, error in
            if let _ = share, error == nil {
                rootRecordID = metadata.rootRecordID
            }
        }
        
        // If the operation fails, return the error to the caller.
        // Otherwise, return the record ID of the share's root record.
        operation.acceptSharesCompletionBlock = { error in
            if let error = error {
                completion(.failure(error))
            } else {
                completion(.success(rootRecordID))
            }
        }
        
        // Set an appropriate QoS and add the operation to the
        // container's queue to execute it.
        operation.qualityOfService = .utility
        container.add(operation)
    }
    
    
}
Updated based on Asperi's Answer:
import SwiftUI
import CloudKit
class ShareDataStore: ObservableObject {
    
    static let shared = ShareDataStore() 
    
    @Published var didRecieveShare = false
    @Published var shareInfo = ""
}
@main
struct athlyticSocialTestAppApp: App {
    
    
    @StateObject var shareDataStore = ShareDataStore.shared 
    
    @UIApplicationDelegateAdaptor(AppDelegate.self) var appDelegate
    
    let sceneDelegate = MySceneDelegate()
    
    var body: some Scene {
        WindowGroup {
            ContentView().environmentObject(shareDataStore)
                 .withHostingWindow { window in
                 sceneDelegate.originalDelegate = window.windowScene.delegate
                 window.windowScene.delegate = sceneDelegate
              }
        }
        
    }
    
}
class MySceneDelegate: NSObject, UIWindowSceneDelegate {
    let container = CKContainer(identifier: "iCloud.com...")
    
     var originalDelegate: UIWindowSceneDelegate?
        var window: UIWindow?
        func sceneWillEnterForeground(_ scene: UIScene) {
            print("scene is active")
        }
        func sceneWillResignActive(_ scene: UIScene) {
            print("scene will resign active")
        }
        
    
      // forward all other UIWindowSceneDelegate/UISceneDelegate callbacks to original, like
   func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
    originalDelegate?.scene!(scene, willConnectTo: session, options: connectionOptions)
   }
        func windowScene(_ windowScene: UIWindowScene, userDidAcceptCloudKitShareWith cloudKitShareMetadata: CKShare.Metadata) {
            print("delegate callback called!! ")
            acceptShare(metadata: cloudKitShareMetadata) { result in
                switch result {
                case .success(let recordID):
                    print("successful share!")
                    ShareDataStore.shared.didRecieveShare = true
                    ShareDataStore.shared.shareInfo = recordID.recordName
                case .failure(let error):
                    print("failure in share = \(error)")
                }
            }
        }
}
extension View {
    func withHostingWindow(_ callback: @escaping (UIWindow?) -> Void) -> some View {
        self.background(HostingWindowFinder(callback: callback))
    }
}
struct HostingWindowFinder: UIViewRepresentable {
    var callback: (UIWindow?) -> ()
    func makeUIView(context: Context) -> UIView {
        let view = UIView()
        DispatchQueue.main.async { [weak view] in
            self.callback(view?.window)
        }
        return view
    }
    func updateUIView(_ uiView: UIView, context: Context) {
    }
}