apt-key deprecated - use signed-by

[dnisbet]

Using apt-key gives warnings of deprecation, an often recommended way to specify the key to use is to drop it into /etc/apt/trusted.gpg.d/ which works fine with the current cookbook. However there is a further recommendation to use apt's [signed-by] field (eg https://blog.cloudflare.com/dont-use-apt-key/) but there's no facility in the cookbook to do this.

❔ Possible Solution

A signed-by property detailing the key file that signs for the apt repository.

⤴️ Describe alternatives you've considered

Just use trusted.gpg.d - but this does have it's own caveats, key in that folder is trusted for ALL repo's.