Move DMF message converter in amqp-api (#3143)

- move in amqp to be in single place
- public DmfMessageConverter that could be used everywhere directly (instead of factory methods)
- defualt amqpMessageConverter bean renamed to dmfMessageConverter
- trusted packages configured (for dmfMessageConverter) with hawkbit.dmf.trusted-packages - default hwakbit dmf model package

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

hawkbit-dmf/hawkbit-dmf-api/pom.xml

@@ -30,5 +30,22 @@
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-annotations</artifactId>
         </dependency>
+
+        <!-- DmfMessageConverter dependencies -->
+        <dependency>
+            <groupId>tools.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+            <optional>true</optional>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-beans</artifactId>
+            <optional>true</optional>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.amqp</groupId>
+            <artifactId>spring-amqp</artifactId>
+            <optional>true</optional>
+        </dependency>
     </dependencies>
 </project>

hawkbit-dmf/hawkbit-dmf-api/src/main/java/org/eclipse/hawkbit/dmf/DmfMessageConverter.java

@@ -0,0 +1,45 @@
+/**
+ * Copyright (c) 2026 Contributors to the Eclipse Foundation
+ *
+ * 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
+ */
+package org.eclipse.hawkbit.dmf;
+
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
+import org.springframework.amqp.core.Message;
+import org.springframework.amqp.support.converter.JacksonJsonMessageConverter;
+import tools.jackson.databind.json.JsonMapper;
+
+// - since spring-amqp 4.0.4 not all packages are assumed trusted for type converter (only java.land and java.util)
+// so e need to add hawkbit DMF model package (and eventual extension packages) as trusted
+// - also (again since spring-amqp 4.0.4) the conversion from empty payload fail (which probably is fine since it is JSON)
+// however, (for backward compatibility, e.g. THING_REMOVED doesn't define payload and could be empty byte[]) we assume that
+// empty payload is empty byte[] and not try to convert it to Object (which fail since it is not JSON)
+public class DmfMessageConverter extends JacksonJsonMessageConverter {
+
+    public static final String DMF_JSON_MODEL_PACKAGE = "org.eclipse.hawkbit.dmf.json.model";
+
+    public DmfMessageConverter(final String... trustedPackages) {
+        this(new JsonMapper(), trustedPackages);
+    }
+
+    public DmfMessageConverter(final JsonMapper jsonMapper, final String... trustedPackages) {
+        super(jsonMapper, trustedPackages.length == 0 ? new String[] { DMF_JSON_MODEL_PACKAGE } : trustedPackages);
+    }
+
+    @Override
+    public @NonNull Object fromMessage(@NonNull final Message message, final @Nullable Object conversionHint) {
+        // default converter tries to convert empty body payload to Object (since rabbit 4.0.4)
+        // which probably is correct since it has to be JSON - however, in this case we assume - empty byte[]
+        if (message.getBody().length == 0) {
+            return message.getBody();
+        } else {
+            return super.fromMessage(message, conversionHint);
+        }
+    }
+}