Flesh out docker-compose Cookiecutter template

docker-compose/hooks/pre_gen_project.py

@@ -0,0 +1,9 @@
+import sys
+
+service_slug = "{{ cookiecutter.__service_slug }}"
+component_list_slug = "{{ cookiecutter.__component_list_slug }}"
+context_slug = "{{ cookiecutter.__context_slug }}"
+for v in (service_slug, component_list_slug, context_slug):
+    if not v:
+        print(f"Please answer all prompts with a non-empty string. Aborting and existing 3 ...")
+        sys.exit(3)