Decouple logic to compute default log format from process environment
Currently, the logic that computes the default log format looks directly at the environment variables from the current process. The playbook builder is designed to be decoupled from the process environment. Thus, this logic is breaking that encapsulation. The logic should instead look at the env object passed to the buildPlaybook
function (which is usually process.env, but not always).
The way to implement this is to set the default value to "auto", the check for this value in the built-in beforeValidation handler and perform the logic there, where the env object passed to buildPlaybook is available.