Add one or more items to the bill of materials for a version of a PCB project.

For each item you can specify:

• part
  Required. The part/designator (e.g. 'C1') for the item.

• value
  The value (e.g. '1K') for the item.

• package
  The package type (e.g. '0402') for the item.

• populate
  Whether or not this part should be populated on the board. Defaults to true.

• mpn
  The manufacturer part number of the part to use for this item. MacroFab assigns the item an
  approved vendor list (AVL) containing the matching part.

• approved_vendor_list_id
  An existing approved vendor list to source this item from, instead of mpn.

Every item is assigned an AVL when it is saved. Responds with the saved items, including their
record_num and approved_vendor_list_id.

New items are sourced by MacroFab. To mark items as customer-supplied, use
PUT /api/v3/pcb/{pcb_id}/{pcb_version}/sourcing/defaults. The origin field is deprecated
and not used.