fix(NODE-5550): set AWS region from environment variable for STSClient

[nbbeeken]

Description

What is changing?

• Same as fix(NODE-5551): set AWS region from environment variable for STSClient #3831

Is there new documentation needed for these changes?

What is the motivation for this change?

Release Highlight

Use region settings for STS AWS credentials request

When using IAM AssumeRoleWithWebIdentity AWS authentication the driver uses the @aws-sdk/credential-providers package to contact the Security Token Service API for temporary credentials. AWS recommends using Regional AWS STS endpoints instead of the global endpoint to reduce latency, build-in redundancy, and increase session token validity. Unfortunately, environment variables AWS_STS_REGIONAL_ENDPOINTS and AWS_REGION do not directly control the region the SDK's STS client contacts for credentials.

The driver now has added support for detecting these variables and setting the appropriate options when calling the SDK's API: fromNodeProviderChain().

Important

The driver will only set region options if BOTH environment variables are present. AWS_STS_REGIONAL_ENDPOINTS MUST be set to either 'legacy' or 'regional', and AWS_REGION must be set.

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• Ran npm run check:lint script
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• Changes are covered by tests
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