Notable changes:
* backend/s3: Automatic validation of `eu-north-1` region
* backend/s3: Support for `credential_process` handling in AWS configuration file
Updated via:
```
go get github.com/aws/aws-sdk-go@v1.16.4
go get github.com/terraform-providers/terraform-provider-aws@v1.52.0
go mod tidy
go mod vendor
```
After a bunch of recent changes/rebasing our vendored dependencies got a
little out of sync w.r.t transitive dependencies through codebases that
are not themselves Go Modules yet.
Here we upgrade the AWS Go SDK to 1.12.27 and AWS provider to include terraform-providers/terraform-provider-aws#1608.
This includes the capability to use named credentials profiles from the `~/.aws/credentials` file to authenticate to the backend.
* Add aws dms vendoring
* Add aws dms endpoint resource
* Add aws dms replication instance resource
* Add aws dms replication subnet group resource
* Add aws dms replication task resource
* Fix aws dms resource go vet errors
* Review fixes: Add id validators for all resources. Add validator for endpoint engine_name.
* Add aws dms resources to importability list
* Review fixes: Add aws dms iam role dependencies to test cases
* Review fixes: Adjustments for handling input values
* Add aws dms replication subnet group tagging
* Fix aws dms subnet group doesn't use standard error for resource not found
* Missed update of aws dms vendored version
* Add aws dms certificate resource
* Update aws dms resources to force new for immutable attributes
* Fix tests failing on subnet deletion by adding explicit dependencies. Combine import tests with basic tests to cut down runtime.
Radek Simko