Feature/SK-1717 | Start combiner server if run as __main__

[Wrede]

This pull request introduces several configuration and startup changes for the combiner service, focusing on how it loads configuration files, sets environment variables, and starts the service process. The changes improve flexibility and standardization in configuration management and service initialization.

Configuration management improvements:

• Added support for specifying the combiner configuration file path via the FEDN_COMBINER_CONFIG environment variable in fedn/common/config.py, with a default fallback location.
• Updated the combiner YAML templates (config/settings-combiner.yaml.local.template and config/settings-combiner.yaml.template) to include new fields fqdn and secure for more flexible network configuration. [1] [2]

Service startup and Docker integration:

• Modified the combiner service entrypoint in docker-compose.yaml to start the combiner using a Python script (combiner.py) instead of the previous CLI command, and added the FEDN_COMBINER_CONFIG environment variable to the container environment. [1] [2]
• Refactored fedn/network/combiner/combiner.py to load configuration from the file specified by FEDN_COMBINER_CONFIG, validate its existence, and initialize the service using the loaded configuration. [1] [2] [3]

[carl-andersson]

What is the reason behind using this rather then the cli combiner start?

There's now code duplication since the old instructions are still there. Try make them the same