Simplified JpaRolloutManagement, moved rollout handling logic to JpaRolloutHandler (#1094)

* introduce RolloutExecutor
* removed unused method

Signed-off-by: Ahmed Sayed <ahmed.sayed@bosch.io>

hawkbit-repository/hawkbit-repository-api/src/main/java/org/eclipse/hawkbit/repository/RolloutExecutor.java

@@ -0,0 +1,51 @@
+/**
+ * Copyright (c) 2021 Bosch.IO GmbH and others.
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.eclipse.hawkbit.repository;
+
+import static org.eclipse.hawkbit.im.authentication.SpPermission.SpringEvalExpressions;
+
+import org.eclipse.hawkbit.repository.model.Rollout;
+import org.eclipse.hawkbit.repository.model.Target;
+import org.springframework.security.access.prepost.PreAuthorize;
+
+/**
+ * Represents the handler service for creating, deleting, and starting a Rollout
+ */
+@FunctionalInterface
+public interface RolloutExecutor {
+
+    /**
+     * Process rollout based on its current {@link Rollout#getStatus()}.
+     *
+     * For {@link RolloutStatus#CREATING} that means creating the
+     * {@link RolloutGroup}s with {@link Target}s and when finished switch to
+     * {@link RolloutStatus#READY}.
+     *
+     * For {@link RolloutStatus#READY} that means switching to
+     * {@link RolloutStatus#STARTING} if the {@link Rollout#getStartAt()} is set
+     * and time of calling this method is beyond this point in time. This auto
+     * start mechanism is optional. Call {@link #start(Long)} otherwise.
+     *
+     * For {@link RolloutStatus#STARTING} that means starting the first
+     * {@link RolloutGroup}s in line and when finished switch to
+     * {@link RolloutStatus#RUNNING}.
+     *
+     * For {@link RolloutStatus#RUNNING} that means checking to activate further
+     * groups based on the defined thresholds. Switched to
+     * {@link RolloutStatus#FINISHED} is all groups are finished.
+     *
+     * For {@link RolloutStatus#DELETING} that means either soft delete in case
+     * rollout was already {@link RolloutStatus#RUNNING} which results in status
+     * change {@link RolloutStatus#DELETED} or hard delete from the persistence
+     * otherwise.
+     *
+     */
+    @PreAuthorize(SpringEvalExpressions.IS_SYSTEM_CODE)
+    void execute(Rollout rollout);
+}