Drop `python-multipart` dependency

[Kludex]

We should have the multipart parsing on Starlette itself.

[!IMPORTANT]

• We're using Polar.sh so you can upvote and help fund this issue.
• We receive the funding once the issue is completed & confirmed by you.
• Thank you in advance for helping prioritize & fund our backlog.

[nanda-mik]

@Kludex, I'd like to take on this task, please assign me. I've understood the parser classes and written test cases for them. I've also started implementing the parser functionality to phase out the dependency on python-multipart. I will try to complete this in some days and will submit a PR then.

Could you provide any specific things or best practices I should follow during the implementation? Additionally, would it be preferable to push the entire change at once or make smaller, incremental PRs?

Thanks!

[rafalkrupinski]

what's wrong with python-multipart?

[Kludex]

Nothing.

[adriangb]

I think the point is that even if nothing is wrong with it Starlette should still absorb that functionality since it's quite core to what Starlette does.

[rafalkrupinski]

I'd rather extract functions like this from existing projects, for greater modularization and to facilitate re-use, but you be you.