Add conditional validation, allow sending empty capacity scaler for r…

…egional backend service (#3033) (#9)

* fix region backend service capacity scaler

* add capacity scaler to fr example

* remove recopied handwritten test

* move constant list into expanders for tpg conversion

* change licenses

Signed-off-by: Modular Magician <[email protected]>

.changelog/3033.txt

@@ -0,0 +1,9 @@
+```release-note:breakingchange
+compute: Added conditional requirement of `google_compute_**region**_backend_service` `backend.capacity_scaler` to no longer accept the API default if not INTERNAL. Non-INTERNAL backend services must now specify `capacity_scaler` explicitly and have a total capacity greater than 0. In addition, API default of 1.0 must now be explicitly set and will be treated as nil or zero if not set in config.
+```
+```release-note:bug
+compute: Fixed `google_compute_**region**_backend_service` so it no longer has a permadiff if `backend.capacity_scaler` is unset in config by requiring capacity scaler. 
+```
+```release-note:bug
+compute: Fixed `backend.capacity_scaler` to actually set zero (0.0) value.
+```

region_backend_service_basic/main.tf

@@ -1,13 +1,13 @@
 resource "google_compute_region_backend_service" "default" {
-  name                            = "region-backend-service-${local.name_suffix}"
+  name                            = "tf-test-rbs-${local.name_suffix}"
   region                          = "us-central1"
   health_checks                   = [google_compute_health_check.default.self_link]
   connection_draining_timeout_sec = 10
   session_affinity                = "CLIENT_IP"
 }
 
 resource "google_compute_health_check" "default" {
-  name               = "health-check-${local.name_suffix}"
+  name               = "tf-test-hc-${local.name_suffix}"
   check_interval_sec = 1
   timeout_sec        = 1