Ignore whitespaces when decoding cookie's content

[RudolfMan]

Our Rails 4 application encodes cookie with Marshal and for some reason its encoded value consists of newlines (\n)
By default Base.decode64/1 throws an ArgumentError

iex> content = "BAh7BkkiD3Nlc3Npb25faWQGOgZFVEkiKTk5ZDQ3YzdiLTdlODItNGUxZS1h\nYTMyLWE4MjIwOWVhNDA5ZQY7AFQ=\n"
iex> Base.decode64!(content)
** (ArgumentError) non-alphabet digit found: "\n" (byte 10)
    (elixir 1.11.0) lib/base.ex:1002: Base.dec64/1
    (elixir 1.11.0) lib/base.ex:1018: Base."-do_decode64/2-lbc$^0/2-0-"/2
    (elixir 1.11.0) lib/base.ex:1012: Base.do_decode64/2

That issue is easily fixed with passing ignore: :whitespace option to Base.decode64!

iex> Base.decode64!(content, ignore: :whitespace) |> ExMarshal.decode()
%{"session_id" => "99d47c7b-7e82-4e1e-aa32-a82209ea409e"}

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Plus as a bonus I use with to avoid nested condition