Add lifecycle ignore changes param for serverless_negs/url_maps

[clement-chaneching]

TL;DR

I would like to be able to ignore changes to the URL_MAP when adding some new route paths.
This is because I manage my load balancer via terraform, but I am dynamically managing some routes using the gcloud CLI, and dont want to override my existing rules when applying my terraform.

Terraform Resources

Add this in in https://github.com/terraform-google-modules/terraform-google-lb-http/blob/main/modules/serverless_negs/main.tf

  lifecycle {
    ignore_changes = [
      host_rule,
      path_matcher,
    ]
  }

In this block:

resource "google_compute_url_map" "default" {
  provider        = google-beta
  project         = var.project
  count           = var.create_url_map ? 1 : 0
  name            = "${var.name}-url-map"
  default_service = google_compute_backend_service.default[keys(var.backends)[0]].self_link
}

Detailed design

This is because terraform doesnt support lifecycle rules at module level.
A solution would be to implement a param: ignore_url_map_changes : bool, and add the above block if true.
Something like : (not tested)

resource "google_compute_url_map" "default" {
  provider        = google-beta
  project         = var.project
  count           = var.create_url_map ? 1 : 0
  name            = "${var.name}-url-map"
  default_service = google_compute_backend_service.default[keys(var.backends)[0]].self_link

  lifecycle {
    ignore_changes = var.ignore_url_map_changes ? [
      host_rule,
      path_matcher,
    ] : []
  }
}

Additional information

I know the module supports the possibility to create a custom url_map and specify it, but it is not really clear to me how I should do it since both URL_map and the serverless_neg module require a default backend.
And it would be the same URL_map with my ignore parameters, and ill be dealing with two backends, and will also need to recreate all my routes.
So it would be useful if a simple ignore param based on a variable could be added.
Thanks for the help!