Return the response body in HTTPUpgradeError "notAnUpgrade"

[mefsantos]

What do you want to happen?

I would like to receive the response body whenever an upgrade error occurs

What happens now?

until version 4.0.6, the HTTPUpgradeError.notAnUpgrade provides the response code and headers

Demo Code

Any demo code that may used to implement/use the desired feature.

Describe alternatives you've considered

add an additional associated value to the enum like: notAnUpgrade(Int, [String: String], Data?)

Additional context

Some times, additional context can be provided in upgrade error responses via the response body which, is currently unaccessible