feat: Support DMS Endpoint Postgres Settings about IAM authentication

[nlpersimon]

Description

Support authentication_method and service_access_role_arn for DMS endpoint postgres settings.
The setting was supported from 6.5 for IAM authentication.

• Add authentication_method and service_access_role_arn to postgres_settings for aws_dms_endpoint hashicorp/terraform-provider-aws#43440
• https://registry.terraform.io/providers/hashicorp/aws/6.5.0/docs/resources/dms_endpoint

Motivation and Context

I am trying to set up a DMS module with IAM-authenticated postgres source endpoint.

Breaking Changes

No.

How Has This Been Tested?

• I have updated at least one of the examples/* to demonstrate and validate my change(s)
• I have tested and validated these changes using one or more of the provided examples/* projects

• I have executed pre-commit run -a on my pull request

[rsi-mrobinson]

@nlpersimon if this change bumps the required aws provider version to >= 6.0 it should also make the required attribute changes for that provider. Ex data.aws_region.current.name becomes data.aws_region.current.region

[nlpersimon]

@nlpersimon if this change bumps the required aws provider version to >= 6.0 it should also make the required attribute changes for that provider. Ex data.aws_region.current.name becomes data.aws_region.current.region

@rsi-mrobinson thanks! I've fixed it in 610c0e8 .

I also checked https://registry.terraform.io/providers/hashicorp/aws/latest/docs/guides/version-6-upgrade for other necessary changes, and data.aws_region.current.name seems to be the only necessary one for this DMS module.