Added the launch_template_custom_user_data variable to the metaflow-computation

[delagoya]

Added the launch_template_custom_user_data variable to the metaflow-computation submodule.
Addresses issue #99

[mt-ob]

I wonder if the variable should expect raw string instead? and we can then use terraform's base64encode. function: https://developer.hashicorp.com/terraform/language/functions/base64encode

so, something along the lines of:

variable "launch_template_custom_user_data" {
  type        = string
  description = "Custom user data script for the launch template provided as a string."
  nullable    = true
  default     = null
}

and

resource "aws_launch_template" "cpu" {
    # ... other configuration ...

    user_data = var.launch_template_custom_user_data != null ? base64encode(var.launch_template_custom_user_data) : null
}

One can then supply the variable as:

  launch_template_custom_user_data = <<-EOF
    #!/bin/bash
    echo "Hello, World!"
    yum update -y
  EOF

[delagoya]

If that makes for a better user experience I think that would be a good change. Will implement and submit a new version after ReInvent.

[delagoya]

Made the changes in the documentation to note that userdata must be MIME encoded and the ec2.tf will base64 encode if defined.