cloud-init: apt can't import key

Hello, I’m using Debian 9.1 x64 and I’m trying to configure my droplet on creation with cloud-init. I want to install multiple package and one of them require a different source and to import a key.

This is done very easily using something like this: https://cloudinit.readthedocs.io/en/latest/topics/examples.html#additional-apt-configuration where you specify a source, a keyserver, and a keyid.

However, this will fail to import the key. gpg will be used to import the key from the server and it requires dirmngr to do so. However in Debian 9.1, dirmngr is not installed (in fact I think the whole thing along with apt-key is deprecated on Debian). So this is a bit problematic. I haven’t found any documentation referring that I can execute things in the order that I want. Cloud-init seems to execute about everything, then the apt module, install packages, then execute custom commands no matter what order I write them in my config file.

Easiest solution would be to install dirmngr first, then let it import the key, then install the rest of the packages that I need. How can I do this?