[java][Jersey2/3] Probe content type for multipart upload parts

[jdimeo]

Many servers throw errors if the multipart upload doesn't correctly identify the part. If a file is passed in to be uploaded, we can use NIO APIs to probe the content type more specifically. In the case of any error, we fall back to the previous default MediaType.APPLICATION_OCTET_STREAM_TYPE.

@bbdouglas @sreeshas @jfiala @lukoyanov @cbornet @jeff9finger @karismann @Zomzog @lwlee2608

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[jdimeo]

I notice some tests failed, and it seems related (because it's mentioning an upload of a .png as the last log line) but as far as I can tell, it's not related (since it's in the Typescript test suite).

[wing328]

https://github.com/OpenAPITools/openapi-generator/actions/runs/4692047648/jobs/8317426213?pr=14965

can you please update the samples when you've time?

[jdimeo]

https://github.com/OpenAPITools/openapi-generator/actions/runs/4692047648/jobs/8317426213?pr=14965

can you please update the samples when you've time?

OK I've done that and it looks like all the checks passed. thanks