Add handling of invalid login challenge

internal/handlers/login.go

@@ -109,11 +109,24 @@ func (h *LoginHandler) handleGet(
 ) {
 	loginRequest, err := h.adminClient.GetLoginRequest(admin.NewGetLoginRequestParams().WithLoginChallenge(challenge))
 	if err != nil {
-		h.logger.Warnf("could not get login request for challenge %s: %v", challenge, err)
+		h.logger.WithError(err).WithField(
+			"challenge", challenge,
+		).Warn("could not get login request for challenge")
 
-		var e *admin.GetLoginRequestGone
-		if errors.As(err, &e) {
-			w.Header().Set("Location", *e.GetPayload().RedirectTo)
+		var notFound *admin.GetLoginRequestNotFound
+
+		if errors.As(err, &notFound) {
+			w.WriteHeader(http.StatusNotFound)
+
+			http.Error(w, notFound.GetPayload().ErrorDescription, http.StatusNotFound)
+
+			return
+		}
+
+		var gone *admin.GetLoginRequestGone
+
+		if errors.As(err, &gone) {
+			w.Header().Set("Location", *gone.GetPayload().RedirectTo)
 			w.WriteHeader(http.StatusGone)
 
 			return