Add bucket_create to modules/gcs (#2827)

* Add `bucket_create` to `modules/gcs`

* Create local with bucket name

* Update variable description

* Fix bucket output

* Fix tests

* Fix tests

* Bump OpenTofu to 1.9.0 (needed for multi-var validations)

modules/gcs/variables.tf

@@ -1,5 +1,5 @@
 /**
- * Copyright 2024 Google LLC
+ * Copyright 2025 Google LLC
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,6 +20,12 @@ variable "autoclass" {
   default     = null
 }
 
+variable "bucket_create" {
+  description = "Create bucket."
+  type        = bool
+  default     = true
+}
+
 variable "cors" {
   description = "CORS configuration for the bucket. Defaults to null."
   type = object({
@@ -168,7 +174,11 @@ variable "lifecycle_rules" {
 variable "location" {
   description = "Bucket location."
   type        = string
-  # default     = "EU"
+  default     = null
+  validation {
+    condition     = ((var.bucket_create == true) == (var.location != null))
+    error_message = "Bucket location is required if and only if bucket_create is true."
+  }
 }
 
 variable "logging_config" {