@type t() :: %ExNylas.CustomAuthentication.Build.Settings{
  credential_id: String.t() | nil,
  email_address: String.t() | nil,
  imap_host: String.t() | nil,
  imap_password: String.t() | nil,
  imap_port: non_neg_integer() | nil,
  imap_username: String.t() | nil,
  refresh_token: String.t() | nil,
  smtp_host: String.t() | nil,
  smtp_port: non_neg_integer() | nil
}