Bill of materials

TASK: Harness bill of materials.

Roll this harness up into a BOM: one line per part number with its total quantity.
- Connector housings: one per connector that at least one wire lands on (connectors no wire reaches are not in this harness).
- Terminals and seals: one per wire end that lands in a connector cavity, using the part numbers given on that end.
- Splices: one per splice that at least one wire end lands on.
- Cavity plugs: every EMPTY cavity of a SEALED connector in this harness takes one plug; plug part number by series: {"DTM":"CP-DTM","DT":"CP-DT","MX150":"CP-MX150"}.
  A cavity is empty if no wire end lands in it.
- Wire: part number "W-<gauge>-<color>", quantity in METRES = total cutMm of those wires / 1000.

Connectors:
[
  {"ref":"X1","pn":"H-DTM-6","series":"DTM","cavities":6,"sealed":true},
  {"ref":"X2","pn":"H-DT-12","series":"DT","cavities":12,"sealed":false},
  {"ref":"X3","pn":"H-DTM-12","series":"DTM","cavities":12,"sealed":false}
]

Splices:
[
  {"ref":"SP1","pn":"SPL-BUTT-M"}
]

Wires:
[
  {"id":"W1","gauge":16,"color":"YE","cutMm":365,"ends":[{"ref":"X1","cavity":3,"terminal":"T-DTM-A","seal":"S-DTM-1"},{"splice":"SP1"}]},
  {"id":"W2","gauge":22,"color":"GY","cutMm":1830,"ends":[{"ref":"X3","cavity":10,"terminal":"T-DTM-A","seal":null},{"splice":"SP1"}]},
  {"id":"W3","gauge":20,"color":"BN","cutMm":290,"ends":[{"ref":"X3","cavity":12,"terminal":"T-DTM-A","seal":null},{"ref":"X1","cavity":4,"terminal":"T-DTM-B","seal":"S-DTM-1"}]},
  {"id":"W4","gauge":16,"color":"BK","cutMm":475,"ends":[{"ref":"X3","cavity":2,"terminal":"T-DTM-A","seal":null},{"ref":"X2","cavity":8,"terminal":"T-DT-A","seal":null}]},
  {"id":"W5","gauge":20,"color":"BU","cutMm":1575,"ends":[{"ref":"X1","cavity":2,"terminal":"T-DTM-B","seal":"S-DTM-2"},{"ref":"X2","cavity":6,"terminal":"T-DT-A","seal":null}]},
  {"id":"W6","gauge":20,"color":"WH","cutMm":825,"ends":[{"ref":"X1","cavity":1,"terminal":"T-DTM-B","seal":"S-DTM-2"},{"ref":"X3","cavity":4,"terminal":"T-DTM-B","seal":null}]},
  {"id":"W7","gauge":22,"color":"YE","cutMm":750,"ends":[{"ref":"X2","cavity":10,"terminal":"T-DT-A","seal":null},{"splice":"SP1"}]},
  {"id":"W8","gauge":20,"color":"GN","cutMm":1970,"ends":[{"ref":"X3","cavity":3,"terminal":"T-DTM-B","seal":null},{"ref":"X2","cavity":3,"terminal":"T-DT-B","seal":null}]},
  {"id":"W9","gauge":22,"color":"BN","cutMm":640,"ends":[{"ref":"X1","cavity":6,"terminal":"T-DTM-A","seal":"S-DTM-1"},{"ref":"X3","cavity":1,"terminal":"T-DTM-A","seal":null}]},
  {"id":"W10","gauge":18,"color":"GN","cutMm":260,"ends":[{"ref":"X2","cavity":5,"terminal":"T-DT-B","seal":null},{"splice":"SP1"}]}
]

Output format (JSON, exactly these keys):
```json
{
 "bom": [
  {
   "pn": "H-DTM-6",
   "qty": 2
  },
  {
   "pn": "W-18-RD",
   "qty": 4.35
  }
 ]
}
```