Add AWS_DYNAMODB_REGION Environment variable

[sergeylanzman]

From eks 1.18 AWS_REGION and AWS_DEFAULT_REGION auto inject to pods. So if you can't use dynamodb table from other region it's read from AWS_REGION always and override on config file. Reorder setting can be break current vault settings. I added one new with AWS_DYNAMODB_REGION

aws/amazon-eks-pod-identity-webhook#40

fix #15071

changelog

storage/dynamodb: Added `AWS_DYNAMODB_REGION` environment variable

[hashicorp-cla]

All committers have signed the CLA.

[heatherezell]

Hi! Can you please also open and link a GitHub issue? Please don't forget a changelog entry, too. Thanks! :)

[sergeylanzman]

@hsimon-hashicorp Added issue. How I can add changelog? can you point me to example?

[heatherezell]

@hsimon-hashicorp Added issue. How I can add changelog? can you point me to example?

Thank you for the issue! Adding a changelog entry is described in the CONTRIBUTING.md. Thanks! :)

[swenson]

LGTM

This seems pretty reasonable to me. Thanks for this!

[swenson]

Oops, I just saw the extra empty lines in the changelog file. Please remove those.

Missed blank lines

[sergeylanzman]

Done

[swenson]

LGTM

[calvn]

@swenson I wonder if using a switch is cleaner instead of deep nesting. I know that we have this pattern for the other config params, but since we're evaluating several env vars for this one it might not be a bad idea?

	var region string
	switch {
	case os.Getenv("AWS_DYNAMODB_REGION") != "":
		region = os.Getenv("AWS_DYNAMODB_REGION")
	case os.Getenv("AWS_REGION") != "":
		region = os.Getenv("AWS_REGION")
	case os.Getenv("AWS_DEFAULT_REGION") != "":
		region = os.Getenv("AWS_DEFAULT_REGION")
	case conf["region"] != "":
		region = conf["region"]
	default:
		region = DefaultDynamoDBRegion
	}

[swenson]

Oh, I was thinking that the deep nesting was a little bit much. The switch is much cleaner.