The new config loader requires some steps to happen in a different
order, particularly in regard to knowing the schema in order to
decode the configuration.
Here we lean directly on the configschema package, rather than
on helper/schema.Backend as before, because it's generally
sufficient for our needs here and this prepares us for the
helper/schema package later moving out into its own repository
to seed a "plugin SDK".
Since the DynamoDB table used by the S3 backend is no longer only used
for locks, rename it in the config to remove any confusion about it
being lock-specific.
The S3 client can return (nil, nil) when the remote state doesn't exist.
The caused a nil pointer dereference when checking the payload.MD5
against the expected value.
This can happen if the remote state was manually removed, but the digest
entry was left in the DynamoDB table.
Updates to objects in S3 are only eventually consistent. If the
RemoteClient has a DynamoDB table available, use that to store a
checksum of the last written state, so the object can be verified by the
next client to call Get.
Terraform currently doesn't have any sort of user feedback around
RefreshState/Get, so we poll only for a short time before returning an
error.
Move the S3 State from a legacy remote state to an official backend.
This increases test coverage, uses a set schema for configuration, and
will allow new backend features to be implemented for the S3 state, e.g.
"environments".
Martin Atkins