Allow setting `chunk_size` for `Response.iter_bytes()` etc...

Requests allowed setting chunk_size within .iter_content() which is currently not an option for our alternatives .stream() and .stream_text().

For .stream_text() we should go the extra step and fix the issue that users sometimes run into when using this feature and use chunk-size for measuring the decoded text, not the raw bytes.

[florimondmanca]

@b0g3r Careful that we’re in a sort of transition state w.r.t. urllib3 usage due to #804 (we’ll soon use our own sync implementation, though keeping urllib3 as an option). Due to this I wouldn’t advise relying on any existing urllib3 functionality — also because we’d want to provide chunk sizing on the async layer too, and it’d be odd to have a different implementation on both sides.

I think we want to look at controlling the chunk size directly from response.iter_bytes()/response.aiter_bytes(), instead…

[florimondmanca]

Hi @b0g3r! I think this is still something we’d like to have, and given discussions in https://github.com/python-gitlab/python-gitlab/pull/1036 it seems like some folks would like to see it too. 😃

Ways to move forward would be:

• Propose an API for this, with context on the existing API on Requests
• Investigate implementation details (ie how are we going to split chunks: buffering, other? Looking at how Requests/urllib3 do this can help)
• Draft a PR 😃