[nandanau]

Summary

• Wrong string comparison: getMediaType used == to compare strings (compares references, not values — always false at runtime), so the image branch was never taken
• Wrong MIME types: Images were returning image/jpg (invalid) instead of image/jpeg, and PDFs were returning image/pdf instead of application/pdf
• Duplicate file field: fileRequestBody added the file both as a proper multipart file part and again as a plain string form-data part because the iterator loop didn't skip the "file" key

Changes

• Use .equals() for string comparison in getMediaType
• Add .toLowerCase() so extension matching is case-insensitive
• Fix MIME types: image/jpeg for images, application/pdf for PDFs
• Skip the "file" key in the form-data loop to prevent adding it twice

Test plan

• Upload a .jpg/.jpeg/.png/.jfif file — verify Content-Type is image/jpeg
• Upload a .pdf file — verify Content-Type is application/pdf
• Inspect the multipart request body — verify the file field appears exactly once (as a file part, not also as a string part)