Asynchronously create many candidate profiles in a single call, typically for HRIS sync workflows that create a batch of candidates at once. Each item follows the same shape as POST /v3/candidates, with first_name and last_name required; all other profile fields are optional. Pass a nested application object to create the candidate's first application — supply a job_id to create an applicant, or a prospect_pool_id (and omit job_id) to create a prospect. A bulk_action_uuid is returned immediately. Per-item success or failure is reported through GET /v3/bulk_requests/{bulk_action_uuid}.