Formatter is very fragile

https://github.com/pinojs/pino/blob/master/docs/api.md#messagekey-string

Configuring `messageKey` will cause the formatter to fail.

Additionally we configure a formatter for `level` which returns `status`, to meet Datadog's expectations https://docs.datadoghq.com/logs/log_configuration/attributes_naming_convention/#reserved-attributes.

``` formatters: {
level: (label: string) => ({
status: label,
}),
},
```