feat: Add engine and engine_version_actual outputs

[stefan-matic]

Description

Added new outputs for engine and engine_version_actual in module, examples, and README.

Motivation and Context

The output value for engine is needed when creating Secrets Manager RDS Credentials in the same way how it's created via the console. The keys that are created by default through the console are:

• username
• password
• engine
• host
• port
• dbname
• dbInstanceIdentifier

When replicating the same approach via Terraform only the engine cannot be sourced using outputs.

resource "random_password" "master" {
  length           = 16
  special          = true
  override_special = "_!%^"
}

resource "aws_secretsmanager_secret" "rds_credentials" {
  name = "rds-credentials"
}

resource "aws_secretsmanager_secret_version" "rds_credentials" {
  secret_id     = aws_secretsmanager_secret.rds_credentials.id
  secret_string = jsonencode(
    {
      "username": "${module.db.db_instance_username}",
      "password": "${random_password.master.result}",
      "engine": "postgres",
      "host": "${module.db.db_instance_address}",
      "port": "${module.db.db_instance_port}",
      "dbname": "${module.db.db_instance_name}"
      "dbInstanceIdentifier": "${module.db.db_instance_id}"
    }
  )
}

Breaking Changes

No.

How Has This Been Tested?

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

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

[antonbabenko]

LGTM. Could you also add one more related output - engine_version_actual ?

[stefan-matic]

@antonbabenko Added the engine_version_actual as output db_instance_engine_version

[bryantbiggs]

Thanks for the PR @stefan-matic - looks great

[antonbabenko]

This PR is included in version 4.4.0 🎉

[github-actions]

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