Newer versions of the Docker Engine have deprecated the version property in Docker Compose. To avoid warnings, we removed the version property from all Compose files, including compose.yaml and compose.dev.yaml.

As a result, users on older Docker Engine versions have reported errors like:

ERROR: The Compose file './compose.yaml' is invalid because:
services.apiserver.expose is invalid: should be of the format 'PORT[/PROTOCOL]'

This occurs because older Docker Engine versions don't support the new expose format used in these Compose files.

Task

We need to:

• Research and test the minimum Docker Engine version that can successfully run Fonoster.
• Update the "Prerequisites" in the self-hosting documentation to reflect this minimum version requirement.
• (Optional) Note that while users on older Docker versions might consider adding back the version field to their Compose files, we strongly recommend upgrading to a newer Docker version for better compatibility and fewer warnings.