Webapp: Design and provide an API to automatically generate and attach a letsencrypt cert

[saarasio]

We have the domain name and we can try and automatically generate a let's encrypt certificate

[saarasio]

Followed instructions here -

https://certbot.eff.org/lets-encrypt/ubuntuxenial-other

And output of these commands and cert generation is captured in this commit -

9c640d1