Use fingerprinting to ensure that the latest version of static files are always used by the users
We were bitten several times those last few days by out-of-date JS and CSS files being used by the browsers.
A quick search revealed that the solution to this problem is called fingerprinting (https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/http-caching?hl=en#invalidating-and-updating-cached-responses)
In short: in the HTML pages, instead of importing toolchains/js/models.js we should import toolchains/js/models.js?v4, with the version number changing at each release.
The server will not care about the ?v4 part, but the browser will see it as a totally new URL, not already in its cache.
I am a bit surprised that the django.contrib.staticfiles app doesn't support that option...