docker-compose.bootstrap.yml leaves orphaned containers

WARNING: Found orphan containers (cert, conf) for this project. If you removed or renamed this service in your compose file, you can run this command with the --remove-orphans flag to clean it up.

Definition of Done:

• fix docker-compose.bootstrap.yml to delete containers cert and conf directly after their commands exit --> currently not possible
• add instruction to README how to achieve this anyways.

Hints:

• none...