Handle OIDC cancellation and workaround missing progress when linking a new device. (#4935)

* Fix a bug where the link device flow wasn't dismissed when complete.

* Listen for cancellation of the WAS when linking a device (dismissing the QR screen when it happens).

* Add CustomStringConvertible conformances to QRCodeLoginScreen actions.

ElementX/Sources/Screens/Settings/AccountSettings/OIDCAccountSettingsPresenter.swift

@@ -20,21 +20,39 @@ class OIDCAccountSettingsPresenter: NSObject {
     private let presentationAnchor: UIWindow
     private let oidcRedirectURL: URL
     
-    init(accountURL: URL, presentationAnchor: UIWindow, appSettings: AppSettings) {
+    typealias Continuation = AsyncStream<Result<Void, OIDCError>>.Continuation
+    private let continuation: Continuation?
+    
+    init(accountURL: URL, presentationAnchor: UIWindow, appSettings: AppSettings, continuation: Continuation? = nil) {
         self.accountURL = accountURL
         self.presentationAnchor = presentationAnchor
         oidcRedirectURL = appSettings.oidcRedirectURL
+        self.continuation = continuation
         super.init()
     }
     
     /// Presents a web authentication session for the supplied data.
     func start() {
-        let session = ASWebAuthenticationSession(url: accountURL, callback: .oidcRedirectURL(oidcRedirectURL)) { _, _ in }
+        let session = ASWebAuthenticationSession(url: accountURL, callback: .oidcRedirectURL(oidcRedirectURL)) { [continuation] _, error in
+            guard let continuation else { return }
+            
+            if error?.isOIDCUserCancellation == true {
+                continuation.yield(.failure(.userCancellation))
+            } else {
+                let errorDescription = error.map(String.init(describing:)) ?? "Unknown error"
+                MXLog.error("A web authentication session error occurred: \(errorDescription)")
+                continuation.yield(.failure(.unknown))
+            }
+            
+            continuation.finish()
+        }
+        
         session.prefersEphemeralWebBrowserSession = false
         session.presentationContextProvider = self
         session.additionalHeaderFields = [
             "X-Element-User-Agent": UserAgentBuilder.makeASCIIUserAgent()
         ]
+        
         session.start()
     }
 }