Previously we encouraged users to import a resource and _then_ write the
configuration block for it. This ordering creates lots of risk, since
for various reasons users can end up subsequently running Terraform
without any configuration in place, which then causes Terraform to want
to destroy the resource that was imported.
Now we invert this and require a minimal configuration block be written
first. This helps ensure that the user ends up with a correlated resource
config and state, protecting against any inconsistency caused by typos.
This addresses #11835.
We're going to use config to determine provider dependencies, so we need
to always provide a config when instantiating a context or we'll end up
loading no providers at all.
We previously had a test for running "terraform import -config=''" to
disable the config entirely, but this test is now removed because it makes
no sense. The actual functionality its testing still remains for now,
but it will be removed in a subsequent commit when we start requiring that
a resource to be imported must already exist in configuration.
Martin Atkins