fix(files): support filename for stream and byte-array multipart uploads

[bsaptarshi]

Summary

Fixes multipart upload behavior for stream/byte file inputs by ensuring a filename is always present.

This addresses #284, where uploads using anonymous bytes/streams (for example, browser recordings) can fail because multipart filename is omitted.

Changes

1) Explicit filename overloads

Added filename-aware overloads in:

• com.openai.models.files.FileCreateParams
• com.openai.models.containers.files.FileCreateParams

New overloads:

• file(InputStream file, String filename)
• file(byte[] file, String filename)

2) Default filename fallback for anonymous uploads

Updated single-argument overloads to provide a safe default filename:

• file(InputStream) now defaults to file.bin
• file(byte[]) now defaults to file.bin

This keeps backward compatibility while improving behavior for anonymous stream/bytes sources.

3) Existing behavior retained

• file(Path) behavior is unchanged and continues to use path.name as filename.
• Multipart content type for binary file parts remains application/octet-stream.

4) Tests

Added/updated tests to verify:

• default filename (file.bin) is applied for single-arg stream/bytes uploads
• explicit filename is preserved when provided
• multipart field content type remains application/octet-stream

Why

file(Path) already included multipart filename metadata, but file(InputStream) and file(byte[]) previously did not.
Some server-side file handling expects filename in multipart parts, causing failures for anonymous stream/bytes uploads.

Validation

Ran targeted tests for modified models:

./gradlew :openai-java-core:test \
  --tests com.openai.models.files.FileCreateParamsTest \
  --tests com.openai.models.containers.files.FileCreateParamsTest

[bsaptarshi]

Hi @TomerAberbach,

Following up on Issue #284. I have added this PR to include default filename fallbacks (file.bin) for InputStream and byte[] overloads, plus new explicit filename overloads.

This should resolve the 400 errors for anonymous uploads while remaining backward compatible. Please help review the changes!

[bsaptarshi]

One more thing to add regarding the test failures. I confirmed they are unrelated to this PR and were already present on upstream/main.

I ran full tests on both:

• upstream/main (without this change)
• this branch (with this change)

The same baseline admin/org failures appear in both runs.
This PR only changes multipart filename handling for stream/byte uploads and related tests.

[bsaptarshi]

Hi @TomerAberbach

Can you or someone take a look at this PR? If it's no.longer required feel free to update the issue and I'll retract this. Not sure what the plan is for this one.

[jbeckwith-oai]

Two blockers:

1. openai-java-core/src/main/kotlin/com/openai/models/files/FileCreateParams.kt:156 — file.bin is not a safe default for this endpoint. The model documentation immediately above says both Fine-tuning and Batch only accept .jsonl, and the README’s anonymous-stream example uses FilePurpose.FINE_TUNE. With this change, that example sends filename="file.bin", so the API still rejects the request. The new tests even pair FilePurpose.BATCH with file.bin, but only inspect the local MultipartField, masking that the resulting request is invalid. Different purposes require different extensions, so there is no universal fallback here. Please keep the explicit filename overloads, avoid presenting file.bin as a safe default for /files, and update the README/examples to use the new filename-aware overload (or otherwise make callers supply a purpose-appropriate filename).

2. openai-java-core/src/test/kotlin/com/openai/models/files/FileCreateParamsTest.kt:107 — the branch fails the repository formatter. ./gradlew :openai-java-core:lintKotlin --no-daemon --no-parallel reports this file; the chained builder call needs ktfmt formatting.

Validation: the two targeted FileCreateParamsTest suites pass, and git diff --check passes, but :openai-java-core:lintKotlin fails as described.