Errors - validate.al

Errors use a non-200 status code and this body:

{
  "detail": {
    "error": "Missing X-API-Key header"
  }
}

Status	`error`	Cause
`400`	`Missing 'email' field in request body`	The JSON body has no `email` field, or the body isn’t JSON.
`400`	`Could not parse email address`	The `email` value couldn’t be read as an address.
`401`	`Missing X-API-Key header`	No API key was sent.
`401`	`Invalid API key`	The key is wrong, was replaced by a new one, or belongs to a deactivated account.
`405`	`HTTP Error 405: METHOD NOT ALLOWED`	The request wasn’t a `POST`.
`502`	(see below)	The validation service didn’t respond. Retry later.

For 502, detail is a string rather than an object: {"detail": "Upstream error: …"}. An address that can’t receive mail is not an error: it returns 200 with a false or text status.