The ignore_changes diff filter was stripping out attributes on Create
but the diff was still making it down to the provider, so Create would
end up missing attributes, causing a full failure if any required
attributes were being ignored.
In addition, any changes that required a replacement of the resource
were causing problems with `ignore_chages`, which didn't properly filter
out the replacement when the triggering attributes were filtered out.
Refs #5627
Here we also introduce a `test` provider meant as an aid to exposing
via automated tests issues involving interactions between
`helper/schema` and Terraform core.
This has been helpful so far in diagnosing `ignore_changes` problems,
and I imagine it will be helpful in other contexts as well.
We'll have to be careful to prevent the `test` provider from becoming a
dumping ground for poorly specified tests that have a clear home
elsewhere. But for bug exposure I think it's useful to have.
Paul Hinze