POST /v2/legal-entities/:id/accounts

Create an account under a legal entity. `excludeFromReporting`
cannot be changed after creation, so set it correctly here.

If `excludeFromReporting` is `true`, the following transaction types
cannot be created against the account: account-interest,
cash-transfer, fee, fx-spot, refund.

Path params:
  id (required) — Legal-entity identifier.

Request:
{
  "data": {
    "type": "account",
    "attributes": {
      "name":                 "string (optional)",
      "externalIdentifier":   "string (required) — bank/custodian-assigned identifier",
      "ccyCode":              "string (required) — ISO 4217",
      "excludeFromReporting": "boolean (optional) — defaults to false"
    },
    "relationships": {
      "depositories": {
        "data": [ { "type": "depository", "id": "string" } ]
      }
    }
  }
}

Response (201 Created):
{
  "data": {
    "id": "string",
    "type": "account",
    "attributes": { /* same as request */ },
    "relationships": {
      "legalEntity":  { "data": { "type": "legal-entity", "id": "string" } },
      "depositories": { "data": [ { "type": "depository", "id": "string" } ] }
    }
  }
}