Missing documentation for how to configure client connection pool

[Discordia]

Issue description

There are some documentation in the configuration reference: https://docs.micronaut.io/latest/guide/configurationreference.html

But there are not documentation for all of the properties. They are listed but sometimes it's just empty under description or it just says "[available in the Netty HTTP client]." Default values are also missing for many.

I would also appreciate a section in this https://docs.micronaut.io/latest/guide/index.html under "7 The HTTP Client" with more in depth on how to configure the http client pool and when it is actually a good idea to do that.