* Respect system/user timezone in API requests
* Fall back to a known timezone if TZ is not set
Co-authored-by: Cristian Dominguez <cristiand391@users.noreply.github.com>
Adding GITHUB_TOKEN & GITHUB_ENTERPRISE_TOKEN support orthogonal to
Config was getting out of hand, especially in `auth` commands that
adjust their messaging and error status based on the presence of these
environment variables.
The new approach builds in support for tokens from environment straight
into Config object by composition. Thus, commands need not ever be
concerned with any specific environment variables.
Due to our HTTP client default behavior, an `Accept` header is added to
all API requests. This is fine for all commands except `gh api`, where
the user should ideally have fine-grained control over most aspects of
HTTP requests and where there should be little to no defaults in general.
