Zaproxy: Add Support for Accept-Encoding: br (Brotli)

[kingthorin]

Per:
https://groups.google.com/a/chromium.org/forum/m/#!msg/blink-dev/JufzX024oy0/WEOGbN43AwAJ

It seems there are Chrome plans to support this encoding type, the post also outlines that Firefox M44 has the support. If client are going to start accepting this encoding type then ZAP probably should as well.

Other references which may be of use or interest:
https://github.com/meteogroup/jbrotli
https://groups.google.com/forum/#!topic/brotli/gGkedK9yHuE

Should maybe be considered in conjunction with: https://github.com/zaproxy/zaproxy/issues/1765

[kingthorin]

In the news http://www.computerworld.com/article/3025456/web-browsers/google-to-boost-compression-performance-in-chrome-49.html

[kingthorin]

FF44 has been released:
https://www.mozilla.org/en-US/firefox/44.0/releasenotes/

Support the brotli compression format via HTTPS content-encoding

[kingthorin]

I don't think this can be tackled as a one-off and I believe that the networking core changes will probably handle this anyway. Also brotli seems to be more applicable for binary data (fonts etc) so probably not as key for ZAP.

@psiinon @thc202 do you think it makes sense to just close this?

[thc202]

It can, the problem is lack of (maintained) encoder.

I'm fine either way.