pub fn harden_prefs_file(app: &AppInfo, key: &str)Expand description
Restrict the on-disk preferences_serde1 file backing key to owner-only
access (Unix mode 0600), warning if it was previously reachable by other
local users.
The cookie/token secret is effectively a master credential (it can forge any
session and mint any token) and the persisted cookie jars hold live session
cookies, so neither should be group- or world-readable. preferences_serde1
creates the file with the process umask (typically 0644); this tightens it
after the fact. No-op on non-Unix platforms, whose permission model differs.