add DummyWorker as workaround for WorkManager bug

dp3t-sdk/sdk/src/main/java/org/dpppt/android/sdk/DP3T.java

@@ -119,6 +119,7 @@ private static void executeInit(Context context, AppConfigManager appConfigManag
 
 		if (appConfigManager.isTracingEnabled()) {
 			SyncWorker.startSyncWorker(context);
+			DummyWorker.startDummyWorker(context);
 			BroadcastHelper.sendUpdateAndErrorBroadcast(context);
 		}
 	}

dp3t-sdk/sdk/src/main/java/org/dpppt/android/sdk/internal/DummyWorker.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2020 Ubique Innovation AG <https://www.ubique.ch>
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ */
+package org.dpppt.android.sdk.internal;
+
+import android.content.Context;
+import androidx.annotation.NonNull;
+import androidx.work.*;
+
+import java.util.concurrent.TimeUnit;
+
+// This DummyWorker is used to be able to start a Worker with
+// ExistingPeriodicWorkPolicy.REPLACE to ensure that the job (and all other jobs) is rescheduled
+// as a workaround for https://issuetracker.google.com/166292069.
+public class DummyWorker extends Worker {
+
+	private static final String WORK_TAG = "DummyWorker";
+
+	public static void startDummyWorker(Context context) {
+
+		Constraints constraints = new Constraints.Builder()
+				.setRequiredNetworkType(NetworkType.CONNECTED)
+				.build();
+
+		PeriodicWorkRequest periodicWorkRequest = new PeriodicWorkRequest.Builder(SyncWorker.class, 1, TimeUnit.DAYS)
+				.setConstraints(constraints)
+				.build();
+
+		WorkManager workManager = WorkManager.getInstance(context);
+		workManager.enqueueUniquePeriodicWork(WORK_TAG, ExistingPeriodicWorkPolicy.REPLACE, periodicWorkRequest);
+	}
+
+	public DummyWorker(@NonNull Context context, @NonNull WorkerParameters workerParams) {
+		super(context, workerParams);
+	}
+
+	@NonNull
+	@Override
+	public Result doWork() {
+		return Result.success();
+	}
+
+}