Function vldb_sqlite_upsert_fts_document_json 

#[unsafe(no_mangle)]
pub extern "C" fn vldb_sqlite_upsert_fts_document_json(
    request_json: *const c_char,
) -> *mut c_char

通过 JSON 请求写入 FTS 文档。 Upsert an FTS document from a JSON request.