Update Neo4j example.

Spring Data Neo4j 6.1 will enforce the usage of
an identifier in relationship properties.
Otherwise unmapped properties of relationships
could get overwritten.

Author: meistermeier

neo4j/example/src/main/java/example/springdata/neo4j/Roles.java

@@ -20,6 +20,8 @@
 import java.util.List;
 
 import org.springframework.data.annotation.PersistenceConstructor;
+import org.springframework.data.neo4j.core.schema.GeneratedValue;
+import org.springframework.data.neo4j.core.schema.Id;
 import org.springframework.data.neo4j.core.schema.RelationshipProperties;
 import org.springframework.data.neo4j.core.schema.TargetNode;
 
@@ -32,6 +34,10 @@
 @RelationshipProperties
 public class Roles {
 
+	@Id
+	@GeneratedValue
+	private Long id;
+
 	private final List<String> roles;
 
 	@TargetNode