Implement Cache-Control: immutable

[mfr-itr]

Steps to reproduce

1. Reload a nextcloud page, for example the Files app

Expected behaviour

The js and css files have a file hash in the URL, for example /css/core/eb4f51d7ec0ed68ba27ebcd1548755aa-server.css?v=a08c1ea900eef4f5e2c1cd1fd55d4117-0. The browser shouldn't have to validate its cache since the file will never change.

Actual behaviour

The browser issues a request, with a 304 response from the server

Solution

Implement the Cache-Control: immutable Cache-Control extension.

Server configuration

Nextcloud version: (see Nextcloud admin page)
12.0.3

Client configuration

Browser: Firefox 57

Operating system: Archlinux

It could also help with #2272.

[rullzer]

I'll look into this for NC14. We have to make sure it also still works in development so that the hash changes often enough (or just not be immutable when we are in debug mode?)

[mfr-itr]

Yes, it should only be on release mode.

[Yamakaky]

In fact, it shouldn't change anything since the hash in the file name changes after each modification. The link in the HTML will change, referencing the new file.
immutable should of course only be enabled for files with a hash in the file name, of course.

[mfr-itr]

Nice!