As an additional security measure, don't use the network version of
setup_14.x. Instead, save nodesource and yarn keys locally and do
the operations in the Dockerfile to install the keys. Then, simply
do the apt install of the dependencies needed from both places.
Keep a copy of the setup_14.x in the data directory as well. In
future, it might be useful to have a script that compares the
versions of that script and keys on the nodesource and yarn websites
— mainly to semi-automatically verify if upstream details have
changed.
