Always flatten http operation input tuples

[petoalbert]

If I define an API for a http operation like this:

Api.get("example" / string / int).query(boolean("a") ++ double("b"))

I would expect the Input type parameter to be like this: (String, Int, Boolean, Double), but instead it would be like this: (String, Int, (Boolean, Double)). That is because query will take a RequestInput[A] where A will already be a tuple in this case, and the implicit zipper will just append this tuple (unflattened) to (String, Int).

This is not an issue of correctness, the DSL is working properly as of now, but I think it would look nicer input types would not be nested like this.