fix: update axum generated multipart requests to own the body

[AlexandreCassagne]

This PR updates axum multipart requests (multipart and multipart-related) to give ownership of the multipart request contents to the application.

The following method on Multipart highlights the need:

pub async fn next_field(&mut self) -> Result<Option<Field<'_>>, MultipartError>

it requires &mut on the multipart argument to allow reading its contents.

In axum documentation, multipart requests are implemented with full ownership (https://docs.rs/axum/latest/axum/extract/struct.Multipart.html).

Taken from the above link, please note the order of parameters is important:

⚠️ Since extracting multipart form data from the request requires consuming the body, the Multipart extractor must be last if there are multiple extractors in a handler. See "the order of extractors"

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[wing328]

thanks for the PR

please run ./bin/generate-samples.sh ./bin/configs/manual/rust-axum-* (using WSL if you're using Windows) to update the samples

[AlexandreCassagne]

@wing328 done, will push. Is there a test that will check that the servers compile and/or successfully produce multipart?

[AlexandreCassagne]

fyi
@linxGnu
@frol @farcaller @richardwhiuk @paladinzh @jacob-pro

[wing328]

yes, there are tests: https://github.com/OpenAPITools/openapi-generator/actions/runs/15116801119/job/42489611479?pr=21301

[wing328]

can you please merge the latest master (upstream official) to your branch, build the CLI JAR locally and regenerate the samples again?

[wing328]

thanks for the PR

cc @linxGnu

[AlexandreCassagne]

@wing328 can anyone other than @linxGnu review if not available?

[wing328]

let's give it a try

thanks again for the PR