Pull request proposal: automatic certificate renewal

Hey Nick (@knolleary),
If you have some time, it would be nice if you could have a look at my last proposal (and Paul's remark about it). When it is ok for you, I will create a pull request because I need certificate renewal to better support a series of new nodes (e.g. my latest node-red-contrib-ui-web-push) which need trusted certificates like e.g. Letsencrypt.
Thanks!!