Requests via httpx

[JR-1991]

Overview

As highlighted and discussed in issue #171, the requests library seems to supply wrong content types, leading to certain upload operations such as replace_datafile not working (see the issue for details). This PR addresses this issue and substitutes requests with httpx that fixes the highlighted problem.

Besides the previously mentioned fix, the library also provides means of async requests as shown here. Since async requests were planned anyway, this would inevitably also lead to ditching requests and thus the change to httpx already paves the way.

Changes introduced by this PR

• Substituted base requests get_request, post_request, put_request and delete_request with httpx requests
• Update requirements to include httpx>=0.26.0
• Added tests for datafile upload and replacement
  • test_file_replacement addresses an example given in issue problem with replace_datafile #171

Additional notes

• Due to httpx supporting Python >3.8, tests for 3.7 had to be removed

Closes

Fixes #171

[JR-1991]

Todo: Add a badge for Python versions supported

[pdurbin]

As discussed, I copied this from https://github.com/gdcc/python-dvuploader (but changed the alt text).

I played a bit with a Markdown version...

![PyPI - Python Version](https://img.shields.io/badge/python-3.8|3.9|3.10|3.11-blue)

... but it's squished together and ugly to add %20 for spaces.

It's interesting that the old badge comes from https://img.shields.io/pypi/pyversions/pydataverse.svg . How are those versions set? 🤔 Should we be updating more files?

[JR-1991]

Thanks for adding the badge @pdurbin !

True that, both ways do not look perfect. As far as I can recall, adding whitespaces is used by most Python repositories (e.g. pyDantic). Shall we stick to the whitespaces?

It's interesting that the old badge comes from https://img.shields.io/pypi/pyversions/pydataverse.svg . How are those versions set? 🤔 Should we be updating more files?

We dont need to specify the version using this badge. It fetches the latest version found on PyPI and puts it there. Pretty smooth 😁

[pdurbin]

As discussed during the https://py.gdcc.io meeting today, tests are passing and we want to add a badge to the README indicating that newer versions of Python are required. I went ahead and added a commit for this and some additional discussion but the PR looks good. Approved!