Using Terraform/HCL as a pre-processor to generate any of the other formats seems like the best now. It is

    - No footguns (compared to the alternatives)
    - Basic text-templating 
    - Can do structural manipulations of data. As opposed to many other config-generators that only
      do string-interpolation of text. Helm and j2.... kill me please, who ever thought this was a good idea
    - Basic looping, transformations and function calls. Without falling into the full imperative 
      programming language trap. Configuration is still deterministic and directed.
    - Supports loading data from other sources
    - Supports comments