Environment variables
OTF can be configured from environment variables. Arguments can be converted to the equivalent env var by prefixing
it with OTF_, replacing all - with _, and upper-casing it. For example:
--secretbecomesOTF_SECRET--site-tokenbecomesOTF_SITE_TOKEN
Env variables can be suffixed with _FILE to tell OTF to read the values from a file. This is useful for container
environments where secrets are often mounted as files.