<@U5V8XNGCX> GsonBuilder is not actually an http4k...

# http4k

[dave]

@joshr GsonBuilder is not actually an http4k class, so we don't provide any docs on it. However, there really isn't much more to configuring the various Json libraries than the Gist shows - you can just extend ConfigurableGson (or Jackson etc) and pass in a custom-configured "core".