[Elixir][Ecto] trim input fields / remove trailing and leading whitespaces with Ecto changeset (User.trim/2)

user.ex

defmodule User do
  use Ecto.Schema
  import Ecto.Changeset
  alias Ecto.Changeset

  schema "users" do
    field :name
    field :email
    field :age, :integer
    field :about
  end

  def changeset(user, params \\ %{}) do
    user
    |> cast(params, [:name, :email, :age, :about])
    |> trim([:name, :email, :about])
    |> validate_required([:name, :email])
  end

  def trim(%Changeset{changes: changes} = changeset, fields) when is_list(fields) do
    changes =
      List.foldl(fields, changes, fn field, changes ->
        value = Map.get(changes, field)
        if is_nil(value), do: changes, else: Map.put(changes, field, String.trim(value))
      end)

    %{changeset | changes: changes}
  end
end