:::endpoint PATCH /v1/me/mail/labels/{id}

One filing system for the whole environment, so this changes what everybody
sees. That is what a shared vocabulary is for, and why there is no per-person
version of it.

Either field on its own is a valid request. Sending neither is not: that would
be a write that changes nothing and answers as though it did.

## Request

```bash
curl -X PATCH https://api.proppertrading.com/v1/me/mail/labels/10 \
  -H "Authorization: Bearer ptat_9f2c1a44_3b8e7d2f5c9a1b4e6d8f0a2c4e6b8d1f" \
  -H "Content-Type: application/json" \
  -d '{"name": "Payout requests"}'
```

| Field   | Type   | Description                                                                                                                     |
| ------- | ------ | ------------------------------------------------------------------------------------------------------------------------------- |
| `name`  | string | Up to 40 characters. Compared without case against the other labels, but never against itself, so recapitalising one is allowed |
| `color` | string | One of `gray`, `red`, `orange`, `amber`, `emerald`, `cyan`, `blue`, `violet`, `pink`                                            |

## Response

```json
{
    "data": {
        "id": 10,
        "object": "mail_label",
        "name": "Payout requests",
        "color": "blue"
    },
    "meta": { "request_id": "req_01kz4bkr1aj1gv63d8fv3133ey" }
}
```

## Errors

| Status | Code                 | Meaning                                                                        |
| ------ | -------------------- | ------------------------------------------------------------------------------ |
| 403    | `insufficient_scope` | This device does not hold `mail:write`                                         |
| 404    | `resource_not_found` | No label with that id in this environment                                      |
| 422    | `validation_failed`  | Neither field was sent, the name is taken, or the colour is not in the palette |