in src/main/java/software/amazon/msk/auth/iam/internals/AWS4SignedPayloadGenerator.java [72:77]
public SdkHttpFullRequest presignRequest(@NonNull AuthenticationRequestParams params) {
SdkHttpFullRequest request = createRequestForSigning(params);
Aws4PresignerParams signingParams = createSigningParams(params);
return Aws4Signer.create().presign(request, signingParams);
}