Elixir: Tesla Middleware of adding content-length header field

ContentLength.ex

defmodule Tesla.Middleware.ContentLength do
  @behaviour Tesla.Middleware

  @impl Tesla.Middleware
  def call(env, next, _options) do
    env
    |> Tesla.put_header(
      "content-length",
      (env.body || "") |> String.length() |> Integer.to_string()
    )
    |> Tesla.run(next)
  end
end