Move awslambda HttpResponseStream/streamifyResponse to the aws-sdk or its own package?

[mbklein]

The fact that streamifyResponse and HttpResponseStream are only available embedded in the runtime makes it difficult to write simple, coherent unit tests for streaming lambda handlers. There's been at least one good attempt to create a wrapper to support easy testing, but it's not completely interface compatible (lacking, for example, the HttpResponseStream.from(underlyingStream, prelude) method) and it seems wasteful to rewrite/repackage code that's already written just to unbundle it from the rest of the NodeJS runtime.

[sladg]

Agreed. Having hard time getting any typings and proper tests. At the same time, it seems like it's still under development and we are experiencing changes in behaviour multiple times a week for a past month. Any more details, examples, etc. would be appreciated.