This sets the `authenticate_box_url` hook as deprecated and also
disables the cloud auth middleware from adding an access token
as a URL parameter by default. An environment variable has been
added which can be used for re-enabling the access token URL
parameter behavior if required for some legacy system which does
not support the authorization header.
Vagrant Core Plugins
These are plugins that ship with Vagrant. Vagrant core uses its own plugin system to power a lot of the core pieces that ship with Vagrant. Each plugin will have its own README which explains its specific role.