Add the option for an additional EBS volume

[JaseKoonce]

As a user of this module, having the option to create a EBS volume in addition to the root volume would be very helpful.

This could be done by adding the following resources:

resource "aws_ebs_volume" "bastion_secondary_ebs_volume" {
  count             = var.enable_secondary_ebs_volume ? 1 : 0
  availability_zone = local.vpc_azs[0]
  size              = 1
  encrypted         = true
  tags              = var.tags
}

resource "aws_volume_attachment" "ebs_attachment" {
  count  = var.enable_secondary_ebs_volume ? 1 : 0
  device_name = "/dev/sdb"
  volume_id   = aws_ebs_volume.bastion_secondary_ebs_volume[0].id
  instance_id = module.bastion.instance_id
}

variable "enable_secondary_ebs_volume" {
  description = "Enable the creation of a secondary EBS volume"
  type        = bool
  default     = true
}

[JaseKoonce]

Changes Merged in.