[FSSDK-12759] fix content-length header in NodeRequestHandler

[raju-opti]

Summary

• prevously, body.length was being used for content-length header, which is incorrect (The length data property of a String value contains the length of the string in UTF-16 code units, we need the byte length of utf-8 endcoded string). This PR fixes it.

Test plan

• added tests
• also tested with real node/python servers

Issues

• FSSDK-12759
• [BUG] Content-Length set from String.length (UTF-16), not UTF-8 byte length — truncates multi-byte request bodies #1155

[Copilot]

Pull request overview

This PR fixes incorrect Content-Length calculation in the Node RequestHandler by switching from UTF-16 code-unit length (string.length) to UTF-8 byte length (Buffer.byteLength), preventing request-body truncation for multi-byte payloads.

Changes:

• Compute content-length using Buffer.byteLength(data) instead of data.length.
• Simplify request body sending by using request.end(data) rather than write() + end().
• Add integration-style tests that POST ASCII, emoji, and CJK JSON to a local HTTP server and assert the full body is received.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
lib/utils/http_request_handler/request_handler.node.ts	Corrects Content-Length to use UTF-8 byte length and sends the body via request.end(data).
lib/utils/http_request_handler/request_handler.node.spec.ts	Adds regression tests using a real local HTTP server to validate multi-byte payloads aren’t truncated.

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[coveralls]

coverage: 77.759% (+0.05%) from 77.713% — raju/content-length-fix into master