Otherwise Nix produces warnings like this:
```
warning: ignoring untrusted substituter 'https://nix-cache.status.im/', you are not a trusted user.
```
Since adding users to `trusted-users` essentially gives them `root`:
>Adding a user to trusted-users is essentially equivalent to giving that user root access to the system.
> — https://nixos.org/manual/nix/stable/command-ref/conf-file.html#conf-trusted-users
A more kosher approach might be to just add the cache config itself globally.
Signed-off-by: Jakub Sokołowski <jakub@status.im>