How to: Update endpoint
The method allows you to update the TXT answer contents of your unique subdomain. Usually carried automatically by automated ACME client.

```POST /update```

#### Required headers
| Header name   | Description                                | Example                                               |
| ------------- |--------------------------------------------|-------------------------------------------------------|
| X-Api-User    | UUIDv4 username received from registration | `X-Api-User: c36f50e8-4632-44f0-83fe-e070fef28a10`    |
| X-Api-Key     | Password received from registration        | `X-Api-Key: htB9mR9DYgcu9bX_afHF62erXaH2TS7bg9KW3F7Z` |

#### Example input
```json
{
    "subdomain": "8e5700ea-a4bf-41c7-8a77-e990661dcc6a",
    "txt": "___validation_token_received_from_the_ca___"
}
```

#### Response

```Status: 200 OK```
```json
{
    "txt": "___validation_token_received_from_the_ca___"
}
```