Update docker-compose version (automatically)

[LeSpocky]

Currently in defaults/main.yml there is docker_compose_version: "1.27.4" and that has to be updated once new releases are published. A bot should do that.

[LeSpocky]

While reading through Dependabot tickets I think, that one does not support it:

1. Support for Docker compose files dependabot/dependabot-core#390
2. Replace package-ecosystem with specifying both language and package-manager in dependabot.yml dependabot/dependabot-core#7189

We need something else here, at least if we don't wanna wait forever for that feature appearing in Dependabot.

[LeSpocky]

The prominent role we borrow from here does not bump docker_compose_version automatically 🤷🏼‍♂️ .

[penguineer]

Question is: Do we need the external docker-compose? Apparently this function has been moved into the docker CLI client and is just provided as an alias now: https://docs.docker.com/compose/migrate/

[24367dfa]

Then lets remove the external component from the role. One less thing to keep up to date.

[LeSpocky]

As far as I understood, docker compose v2 is a plugin now, which has to be installed separately. In the back of my head I remember someone questioned if both are compatible? But if we are currently not using it, we should just start over with v2 once a need rises again.