jsonv2 now returns an error when you marshal or unmarshal a time.Duration
without an explicit format flag. This is an intentional, temporary choice until
the default [time.Duration] representation is decided (see golang/go#71631).
setting.Snapshot can hold time.Duration values inside a map[string]any,
so the jsonv2 update breaks marshaling. In this PR, we start using
a custom marshaler until that decision is made or golang/go#71664
lets us specify the format explicitly.
This fixes `tailscale syspolicy list` failing when KeyExpirationNotice
or any other time.Duration policy setting is configured.
Fixes#16683
Signed-off-by: Nick Khyl <nickk@tailscale.com>
4df02bbb48