Recursively merge .env.yml and .env.yml.d/*.yml into the process environment. Supports YAML anchors and aliases,
which is the big win over straight JSON for configuration files.
The environment configuration file. If it's not mentioned here, it won't be included.
Configuration partials, parsed in natural sort order. Should match glob ??-*.yml, e.g. 00-logging.yml or
99-security.yml. Build up complex configurations here, then reference them in .env.yml.
The test/.env.yml.d/ directory contains some examples.