[#1582] initial draft of CoAP support in Ditto gateway:

* provides (unsecure, plain UDP) CoAP endpoint
* providing equivalent CoAP resources as the HTTP resources:
   * /things, /policies, /whoami
   * supporting verbs: GET, PUT, POST, DELETE, PATCH, IPATCH
* providing "observe" functionality for watching changes of resources

Signed-off-by: Thomas Jaeckle <ditto@jaeckles.de>

base/model/src/main/java/org/eclipse/ditto/base/model/auth/DittoAuthorizationContextType.java

@@ -34,6 +34,13 @@ public final class DittoAuthorizationContextType extends AuthorizationContextTyp
     public static final DittoAuthorizationContextType PRE_AUTHENTICATED_HTTP =
             new DittoAuthorizationContextType("pre-authenticated-http");
 
+    /**
+     * Type indicating that the authorization context was created the pre-authenticated mechanism via CoAP which is
+     * setting an authenticated subject as header field.
+     */
+    public static final DittoAuthorizationContextType PRE_AUTHENTICATED_COAP =
+            new DittoAuthorizationContextType("pre-authenticated-coap");
+
     /**
      * Type indicating that the authorization context was created using the pre-authenticated mechanism of connections
      * by having configured the contained auth subjects in a Ditto connection source/target.

bom/pom.xml

@@ -59,6 +59,7 @@
         <reactive-streams.version>1.0.4</reactive-streams.version>
         <netty-bom.version>4.1.86.Final</netty-bom.version>
         <cloudevents.version>2.3.0</cloudevents.version>
+        <californium.version>3.8.0</californium.version>
 
         <slf4j.version>1.7.36</slf4j.version>
         <logback.version>1.2.11</logback.version>
@@ -263,6 +264,17 @@
                 <version>${cloudevents.version}</version>
             </dependency>
 
+            <dependency>
+                <groupId>org.eclipse.californium</groupId>
+                <artifactId>californium-core</artifactId>
+                <version>${californium.version}</version>
+            </dependency>
+            <dependency>
+                <groupId>org.eclipse.californium</groupId>
+                <artifactId>scandium</artifactId>
+                <version>${californium.version}</version>
+            </dependency>
+
             <!-- ### Indirect "runtime" dependencies we want to pin to a common version -->
             <dependency>
                 <groupId>org.scala-lang</groupId>

gateway/service/pom.xml

@@ -49,6 +49,15 @@
             <scope>runtime</scope>
         </dependency>
 
+        <dependency>
+            <groupId>org.eclipse.californium</groupId>
+            <artifactId>californium-core</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.eclipse.californium</groupId>
+            <artifactId>scandium</artifactId>
+        </dependency>
+
         <dependency>
             <groupId>org.eclipse.ditto</groupId>
             <artifactId>ditto-base-model</artifactId>

gateway/service/src/main/java/org/eclipse/ditto/gateway/service/coap/DittoCoapDeviceInfoSupplier.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2023 Contributors to the Eclipse Foundation
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information regarding copyright ownership.
+ *
+ * This program and the accompanying materials are made available under the
+ * tetms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.eclipse.ditto.gateway.service.coap;
+
+import java.security.Principal;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.eclipse.californium.elements.auth.AdditionalInfo;
+import org.eclipse.californium.scandium.auth.ApplicationLevelInfoSupplier;
+import org.eclipse.ditto.base.model.auth.AuthorizationContext;
+import org.eclipse.ditto.base.model.headers.DittoHeaderDefinition;
+import org.eclipse.ditto.internal.utils.akka.logging.DittoLoggerFactory;
+import org.eclipse.ditto.internal.utils.akka.logging.ThreadSafeDittoLogger;
+
+/**
+ * TODO TJ doc
+ * TODO TJ use in scope of authenticating with PSK / Certificate
+ */
+final class DittoCoapDeviceInfoSupplier implements ApplicationLevelInfoSupplier {
+
+    private static final ThreadSafeDittoLogger LOGGER =
+            DittoLoggerFactory.getThreadSafeLogger(DittoCoapDeviceInfoSupplier.class);
+
+    /**
+     * Creates additional information for authenticated devices.
+     *
+     * @param context the {@link AuthorizationContext} of the authenticated device.
+     * @return additional device information.
+     */
+    public static AdditionalInfo createDeviceInfo(final AuthorizationContext context) {
+        final Map<String, Object> result = new HashMap<>();
+        result.put(DittoHeaderDefinition.AUTHORIZATION_CONTEXT.getKey(), context);
+        return AdditionalInfo.from(result);
+    }
+
+    @Override
+    public AdditionalInfo getInfo(final Principal principal, final Object customArgument) {
+        if (customArgument instanceof AdditionalInfo additionalInfo) {
+            final AuthorizationContext authorizationContext =
+                    additionalInfo.get(DittoHeaderDefinition.AUTHORIZATION_CONTEXT.getKey(), AuthorizationContext.class);
+            LOGGER.info("get AdditionalInfo auth context: {} - for principal: {}", authorizationContext, principal);
+            return additionalInfo;
+        }
+        LOGGER.debug("did not get additional info");
+        return AdditionalInfo.empty();
+    }
+}