Explicitly declare jMolecules DDD dependency.

Fixes GH-3379.

Author: odrotbohm

pom.xml

@@ -324,6 +324,13 @@
 			<scope>test</scope>
 		</dependency>
 
+		<dependency>
+			<groupId>org.jmolecules</groupId>
+			<artifactId>jmolecules-ddd</artifactId>
+			<version>${jmolecules}</version>
+			<optional>true</optional>
+		</dependency>
+
 		<dependency>
 			<groupId>org.jmolecules.integrations</groupId>
 			<artifactId>jmolecules-spring</artifactId>