FeatureRequest: memoryview Response

[j-carson]

I am assembling a large Response content buffer using BytesIO. In order to pass my data to the Response class, I need to make a bytes copy of the buffer. It would be more efficient if the Response class would accept a memoryview, so could use the getbuffer method and avoid this extra copy.

[bschoenmaeckers]

This will be possible after #2577 is merged