fix: add groupId and artifactId variables

Author: sleipnir

java-std/cookiecutter.json

@@ -5,6 +5,9 @@
     "app_image_tag": "ttl.sh/spawn-java-postalcode:1h",
     "app_port": 8091,
     "app_version": "1.0.1",
+    "group_id": "io.eigr.spawn.java",
+    "artifact_id": "demo",
+    "version": "1.0.1",
     "spawn_app_spawn_system": "spawn-system",
     "spawn_app_namespace": "default",
     "spawn_app_statestore_type": "native",