This resurrects the previously documented but unused "project" option.
This option is required to create buckets (so they are associated with the
right cloud project) but not to access the buckets later on (because their
names are globally unique).
* Remove the (unused) "project" option.
* Mark the "credentials" option as optional; document behavior when
unset.
* Mark the "path" option as deprecated (was: legacy) to match
Terraform's terminology.
The backend has been renamed. Using the old name in the config will
trigger a deprecation warning, but the implementation and the
documentation is the same.
Added locking support via blob leasing (requires that an empty state is
created before any lock can be acquired.
Added support for "environments" in much the same way as the S3 backend.
The "terraform init" command has a lot of different functionality now,
making it hard to follow all of the options in the previous presentation.
Instead, here we describe each of the steps and its associated options
separately, hopefully making it easier to understand what each option
relates to.
In addition, much of the detail around backend partial configuration is
factored out into the backend configuration page, where it seems more
"at home"; previously it felt hard to follow exactly how partial
configuration would be used, due to the information on it being split over
two different pages.