service_account_config for Cloud Run v2

Additional changes:
* align vpc-connector interface to Cloud Functions
* split managed and unmanaged resources into separate files, this makes
  easier to introduce further changes
* add support for contexts
* move `vpc_connector` variable to variables.tf for Cloud Functions
* remove `create` from `vpc_connector` in Cloud Functions as it was
  sharing the meaning with `vpc_connector_create`

modules/cloud-run-v2/variables-vpcconnector.tf

@@ -15,7 +15,7 @@
  */
 
 variable "vpc_connector_create" {
-  description = "Populate this to create a Serverless VPC Access connector."
+  description = "VPC connector network configuration. Must be provided if new VPC connector is being created."
   type = object({
     ip_cidr_range = optional(string)
     machine_type  = optional(string)
@@ -37,4 +37,12 @@ variable "vpc_connector_create" {
     }), {})
   })
   default = null
+  validation {
+    condition = (
+      var.vpc_connector_create == null ||
+      try(var.vpc_connector_create.instances, null) != null ||
+      try(var.vpc_connector_create.throughput, null) != null
+    )
+    error_message = "VPC connector must specify either instances or throughput."
+  }
 }