Merge pull request #7 from garutilorenzo/new_features

## New features

* Added EFS for persistent storage via [AWS EFS csi driver](https://github.com/kubernetes-sigs/aws-efs-csi-driver).
* Added the possibility to expose the kubeapi server to the internet. Access is granted only from *my_public_ip_cidr* for security reasons.
* Added Lambda funcion to automatically delete removed nodes from k3s cluster (EC2 spot instances)
* Added *null_resource* to fix Lambda orphan ENI. [Ref.](hashicorp/terraform-provider-aws#10329)

## Minor changes

* Fixed resource tags/names
* Renamed *agent* resources to *worker* resources
* Added SSM Policy to access EC2 from AWS console

## Bug fixes

* Added lifecycle on k3s-workers
* Fix allow_strict security group deletion on apply

Install nginx ingress controller instead of Traefik

Added output in main.tf

Added environment

Moved to terraform module

Terraform fmt