Requests with no body don't sign correctly

[lucix-aws]

Describe the bug

S3Client.createBucket, when called with only a bucket name as input, appears to be signing incorrectly. The service will reject the request claiming that the signature is invalid.

Expected behavior

Bucket should be created.

Current behavior

S3Exception is thrown: The request signature we calculated does not match the signature you provided. Check your key and signing method.

Steps to Reproduce

fun main():Unit = runBlocking {
    S3Client.fromEnvironment().use { s3 ->
        s3.createBucket { bucket = "buckettestdgttxcq" }

        s3.listBuckets {}.buckets?.forEach {
            println(it.name)
        }
    }
}

Possible Solution

No response

Context

No response

AWS Kotlin SDK version used

0.14.0-beta

Platform (JVM/JS/Native)

JVM

Operating System and version

macOS 12.2.1

[lucix-aws]

This happens because we're setting Content-Type even when there's no body. We include that in the set of signed headers, but it looks like services do the calculation without it when the body is empty. So theoretically, any request with no body would fail in this way, not just this particular S3 API.

It appears to actually be a regression. We had previously set Content-Type conditionally - see https://github.com/awslabs/smithy-kotlin/pull/55/files# - but it looks like that code was dropped in later refactors.

[github-actions]

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