Add SSL/TLS configuration for the Loadbalancer

[devraj]

Final piece of the Loadbalancer configuration is provisioning a SSL/TLS certificate from LetsEncrypt. Ideally we want to handle this all on Linode without involving a third party like Cloudflare (for simplicity sake).

[devraj]

Reference docs:

• https://rafrasenberg.com/posts/kubernetes-with-terraform-traefik-v2-cert-manager-part-1/
• https://github.com/rafrasenberg/kubernetes-terraform-traefik-cert-manager