requests: Add context manager for response object.

[Gadgetoid]

Summary

When accessing response.raw it's not always obvious you should call response.close() to close and free the socket. Since lwIP has a five socket limit by default this can very quickly result in cryptic ENOMEM errors.

A context manager is widely understood to handle freeing resources on exit and permits the following, Pythonic pattern without leaking open sockets:

buffer = bytearray(1024)
with requests.get("some-resource") as response:
    while length := response.raw.readinto(buffer)
        output.write(memoryview(buffer)[:length])

While I came up with this idea and wrote this code independently , this PR transpired to be partially a dupe of #278 but I have excluded the iteration features in favour of a clean, concise change in the hope it would be easier to consider.

Testing

This is a minor change adding well understood magic methods, I did a cursory check to make sure it would work.

Trade-offs and Alternatives

This is a very minor change for a lot of potential utility, though without associated documentation changes it's unlikely to receive adoption.

CPython's "requests" library has the concept of a Session, which includes a context manager at a lower level, and implements get/post etc using a transient Session. This is a potentially useful concept in MicroPython because the time cost of re-opening a socket when TLS is involved is prohibitive - 300-400ms. I'm currently using a completely custom HTTP library to avoid this.

This change also has some minor functional overlap with urllib urequest's urlopen which is sometimes favoured for streaming requests.

Generative AI

I did not use generative AI tools when creating this PR.

[agatti]

A bit of a controversial take, but replacing the non-self arguments list with a single *_ saves 28 bytes.

I'd say it's safe to assume that a context manager will always pass the correct arguments to __exit__, although that way will look quite uglier than what you initially wrote :)

[Gadgetoid]

A bit of a controversial take, but replacing the non-self arguments list with a single *_ saves 28 bytes.

I did a quick search of the codebase and picked the most common pattern. I did see *args and my personal preference would probably be _type, _value, _traceback to both flag as unused and keep it unambiguous 😆

Might not hurt to get some consensus on this and raise a PR to make every __exit__ in micropython-lib look the same.