chore: add `taskmaster` env in `FOCA` config

[JaeAeich]

Summary by Sourcery

Add support for Taskmaster environment properties in the FOCA configuration, including new functions to retrieve custom configuration and Taskmaster template.

New Features:

• Introduce taskmaster_env_properties in the custom configuration model to manage Taskmaster environment properties.

Enhancements:

• Add functions to retrieve custom configuration and Taskmaster template from the configuration file.