The roundup-server doesn't set any cache control (max-age, expires)
headers on static files.

This means javascript, image and other static resources have to be
retrieved on each page load.

I think for initial implementation setting a max-age by
data type:

  .js text/javascript maxage=2weeks,
 .css text/css maxage=2months

is sufficient for @@file assets and attached assets.

Also setting a max-age for attached assets otherwise not specified
(e.g. a file attached to an issue accessed via: 
https://mytracker.example.com/demo/file1/android-chrome-192x192.png)
should work for initial implementation.

changeset:   5980:54d0080769f9

implemented the mechanism in the 2.0.0 release.

changeset:   6546:c58c7cd31243

implements the settings for javascript and css files.

closing.

Also as a note this implements Cache-Control with max-age settings. It does not
implement the Expires header.