Add an ImportStateIdFunc field to the ImportState testing functionality.
This will allow for more powerful generation of complex import state IDs
that can't be accomplished by ImportStateId or ImportStateIdPrefix
themselves.
Previously having a config was mutually exclusive with running an import,
but we need to provide a config so that the provider is declared, or else
we can't actually complete the import in the future world where providers
are installed dynamically based on their declarations.
Adds the `ImportStateIdPrefix` field for import acceptance tests. There are (albeit fairly rare) import cases where a resource needs to be imported with a combination of the resource's ID and a known string prefix. This allows the developer to specify the known prefix, and omit the `ImportStateId` field.
```
$ make test TEST=./helper/resource TESTARGS="-run=TestTest_importStateIdPrefix"
==> Checking that code complies with gofmt requirements...
==> Checking AWS provider for unchecked errors...
==> NOTE: at this time we only look for uncheck errors in the AWS package
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/03/30 18:08:36 Generated command/internal_plugin_list.go
go test -i ./helper/resource || exit 1
echo ./helper/resource | \
xargs -t -n4 go test -run=TestTest_importStateIdPrefix -timeout=60s -parallel=4
go test -run=TestTest_importStateIdPrefix -timeout=60s -parallel=4 ./helper/resource
ok github.com/hashicorp/terraform/helper/resource 0.025s
```
James Bardin