ToRaw

Target for implicit conversions to Header.Raw from modelled headers and key-value pairs.

A method taking variadic ToRaw arguments will allow taking heterogeneous arguments, provided they are either:

- A value of type A which has a Header[A] in scope - A (name, value) pair of String, which is treated as a Recurring header - A Header.Raw - A Foldable (List, Option, etc) of the above.