Bulk update portfolios

Asynchronously updates positions and performance for many portfolios at a time.
Submit a batch of portfolios to update and check status of processing using
the /v1/partner/batches endpoint.

Note:

• This endpoint can only be used for updates, sending portfolio ids which have not been
  previously created will cause that task to fail.
• Either id or external_id must be specified for each portfolio.
• Positions are always replaced
• Performance is replaced unless the replace_performance option is set to false