There are a variety of generic DSLs for encoding configuration concisely with composability, functions, custom validation, etc. Some examples would be jsonnet,

There are a variety of generic DSLs for encoding configuration concisely with composability, functions, custom validation, etc. Some examples would be jsonnet, dhall, and cue. If the configuration needs to be transformed into a more computer-friendly format like json or yaml for later loading by a binary, that's easy enough to do at build time in a modern-ish build system like bazel