Normalize data in Ecto before insert to DB

ecto_normalize_data.md

Example code:

def changeset(model, params \\ :empty) do
  model
  |> cast(params, @required_fieds, @optional_fields)
  |> validate_length(:code, is: 2)
  |> normalize_code
end

defp normalize_code(changeset) do
  case changeset do
    %Ecto.Changeset{valid?: true, changes: %{code: code}} ->
      put_change(changeset, :code, String.upcase(code))
    _ ->
      changeset
  end
end