enable gzip and deflate in http client

[jeremyandrews]

• enable gzip support in the http client
• can be disabled with --no-gzip or GooseDefault::NoGzip
• documented how to manually enable deflate and/or brotli compression

[jeremyandrews]

I ran current -dev w/o this patch, and current -dev w/ this patch, each 3 times as follows (restarting all server processes before each batch of 3):

cargo run --release --example drupal_loadtest -- --host http://apache -v -u12 -t10m && sleep 30 && cargo run --release --example drupal_loadtest -- --host http://apache -v -u12 -t10m && sleep 30 && cargo run --release --example drupal_loadtest -- --host http://apache -v -u12 -t10m

Here's the data:
https://docs.google.com/spreadsheets/d/1lsOagHY1yISQ_HcpwbIxoxXx8s2q5KxKYXvZmhgsMYs/edit#gid=0

Goose made >30% more anonymous requests, but 5.6% fewer authenticated requests with this patch applied. Without compression it averaged 6,473 requests per second. With compression it averaged 9,542 requests per second. It would be good to re-run the test with fewer GooseUsers and an evenly balanced number of Anonymous and Authenticated users: my assumption is that the reduction in authenticated traffic is simply because anonymous traffic was being returned so quickly by Varnish that it was getting scheduled far more.

The Apache/Varnish server saw no change in CPU usage (as Varnish caches compressed pages), whereas the Goose server saw an increase in CPU usage, visible here (Goose is running in a 32-core VM):

(On the left is with compression, on the right is without compression: the spike is re-compiling Goose)

Though it made considerably more requests, obviously there was considerably less network traffic generated:

(On the left is without compression, on the right is with compression)

[LionsAd]

Let’s also add the request headers to the debug log and:or add a typical HTTP header to the docs.

[jeremyandrews]

Authenticated requests slow down as Apache is compressing each request due to how my server is configured. There's additional CPU usage showing up on the Apache server because of this.