fix backup selection re-creation

[tchernomax]

fix #48

[lgallard]

@tchernomax thanks for the PR. It seems this new feature was introduced in the AWS provider version 3.72.0.

I see it fixes the issue but I would a moe dynamic solution, similar to the resources attribute:

resources = lookup(element(local.selections, count.index), "resources", null)
not_resources = lookup(element(local.selections, count.index), "not_resources", null)

And include the following to the locals:

  # Selection
  selection = var.selection_name == null ? [] : [
    {
      name           = var.selection_name
      resources      = var.selection_resources
      not_reesouces  = var.selection_not_resources
      conditions     = var.selection_conditions
      selection_tags = var.selection_tags
    }
  ]

And something similar for condition. I'm going to merge your code and implement a dynamic behaviour.