refactor: show failure notification in status bar

Set the notification channel importance to `IMPORTANCE_LOW`.

The new importance is used only after the remote verify job has been
executed once. To fix this, a much larger refactoring would be required.

Author: smdyv

app/src/main/java/app/attestation/auditor/RemoteVerifyJob.java

@@ -55,7 +55,8 @@ public class RemoteVerifyJob extends JobService {
     static final String KEY_INTERVAL = "remote_interval";
     private static final int NOTIFICATION_ID = 1;
     private static final String NOTIFICATION_CHANNEL_SUCCESS_ID = "remote_verification";
-    private static final String NOTIFICATION_CHANNEL_FAILURE_ID = "remote_verification_failure";
+    private static final String NOTIFICATION_CHANNEL_FAILURE_ID = "remote_verification_failure_2";
+    private static final String NOTIFICATION_CHANNEL_FAILURE_ID_OLD = "remote_verification_failure";
 
     static final ExecutorService executor = Executors.newSingleThreadExecutor();
     private Future<?> task;
@@ -213,9 +214,12 @@ public boolean onStartJob(final JobParameters params) {
             successChannel.setShowBadge(false);
             channels.add(successChannel);
 
+            // Raised from IMPORTANCE_MIN to IMPORTANCE_LOW
+            manager.deleteNotificationChannel(NOTIFICATION_CHANNEL_FAILURE_ID_OLD);
+
             final NotificationChannel failureChannel = new NotificationChannel(NOTIFICATION_CHANNEL_FAILURE_ID,
                     context.getString(R.string.remote_verification_notification_failure_channel),
-                    NotificationManager.IMPORTANCE_MIN);
+                    NotificationManager.IMPORTANCE_LOW);
             failureChannel.setShowBadge(false);
             channels.add(failureChannel);