A management API call that did not succeed (sc-1504).

Every EndPointBlank.Management call answers {:error, %Error{}} rather than raising; the stream/… functions raise it, since a stream cannot answer a tuple.

• :code -- the API's stable error.code, a string, for programs to match on ("not_found", "validation_failed", "plan_limit", ...). A code this SDK does not know yet is kept as sent: see known_codes/0. The SDK adds four of its own, for answers that never reached the API or did not come back in its error shape: "transport_error", "unexpected_response", "invalid_request" and "not_available_for_managed_client".
• :message -- for people; it may change.
• :details -- field-level detail when the API sent any (for "validation_failed", the invalid fields), otherwise nil.
• :status -- the HTTP status, or nil when no answer arrived.
• :retry_after -- the Retry-After header in seconds, when sent.
• :location -- the Location header, when sent. A credential POST refused with "idempotency_replay_unavailable" carries the credential's path here.

The management key is never part of an error, and neither is a request or response body other than the API's own error object.

case EndPointBlank.Management.Clients.get(mgmt, id) do
  {:ok, client} -> client
  {:error, %Error{code: "not_found"}} -> nil
  {:error, %Error{code: "rate_limited", retry_after: seconds}} -> ...
end