feat: Add max_throughput to vpc-serverless-connector-beta (#322)

Expose the max_throughput argument of the google_vpc_access_connector.

Author: rsinnet

modules/vpc-serverless-connector-beta/README.md

@@ -23,6 +23,7 @@ module "serverless-connector" {
     machine_type    = "e2-standard-4"
     min_instances   = 2
     max_instances   = 3
+    max_throughput  = 300
   }]
 }
 ```

modules/vpc-serverless-connector-beta/main.tf

@@ -31,7 +31,8 @@ resource "google_vpc_access_connector" "connector_beta" {
       project_id = lookup(each.value, "host_project_id", null)
     }
   }
-  machine_type  = lookup(each.value, "machine_type", null)
-  min_instances = lookup(each.value, "min_instances", null)
-  max_instances = lookup(each.value, "max_instances", null)
+  machine_type   = lookup(each.value, "machine_type", null)
+  min_instances  = lookup(each.value, "min_instances", null)
+  max_instances  = lookup(each.value, "max_instances", null)
+  max_throughput = lookup(each.value, "max_throughput", null)
 }