Introduce inital draft of hawkBit SDK (#1638)

Intends to provide a Java SDK facilitating:
* development of back-end integrations using mgmt api (including UI-s)
* development of java based high-end devices (which could run Spring apps) to communicate with hawkBit via DDI API
* implementation of demo/test cases using device & management SDK

Status: initial draft
 - Feign client did & management API - done
 - Hal/HATEAOS Support - works (including in non-web apps)
 - device communication works when no software updates (e.g. pulling software base)
 - demo for single and multiple devices simulation (including management API uses)
 - TODO - fix software update flows
 - TODO - provide more integration points for developers to interact with device SDK

Signed-off-by: Marinov Avgustin <Avgustin.Marinov@bosch.com>

hawkbit-sdk/hawkbit-sdk-device/src/main/resources/application.properties

@@ -0,0 +1,11 @@
+#
+# Copyright (c) 2023 Bosch.IO GmbH and others
+#
+# This program and the accompanying materials are made
+# available under the terms of the Eclipse Public License 2.0
+# which is available at https://www.eclipse.org/legal/epl-2.0/
+#
+# SPDX-License-Identifier: EPL-2.0
+#
+
+