We shouldn't perform parameter wrapping if it would overwrite one of the
parameters sent with the request, as that would interfere with reading
the parameter directly from the top level `params` hash.

The current implementation has logic for this case, but it doesn't
handle `nil`/`false` values, which means these parameters:

    { "user" => nil }

are transformed into this `params` hash:

    { "user" => { "user" => nil } }

and `params["user"]` no longer returns the original parameter value.