Customer has accountType field but there is no documentation about it

[maznu]

Since Simwood Partner has launched residential offers, we now see a few different values for Customers' "accountType" (excerpt below):

{
  "items": [
    {
      "type": "customer",
      "id": "6626",
      "accountType": "BUSINESS",
    },
    {
      "type": "customer",
      "id": "7741",
      "accountType": "RESIDENTIAL",
    },
    {
      "type": "customer",
      "id": "11379",
      "accountType": "WLR",
    },
  ],
}

1. Currently the API documentation only mentions accountType on Credit Status objects, so please could you document this new field on Customer objects.
2. The differences between BUSINESS and RESIDENTIAL and especially WLR could do with an explanation.

If it wasn't for item 2 above, I'd submit a PR myself — but being unsure why this is a tristate variable, I'm filing this issue instead.

Thanks!