fix(pgsql-subnet) add explicit definition for the automatic action

Signed-off-by: Damien Duportal <damien.duportal@gmail.com>

.gitignore

@@ -10,3 +10,4 @@
 .terraform
 backend-config
 terraform-plan-output.txt
+tfplan

vnets.tf

@@ -59,6 +59,9 @@ resource "azurerm_subnet" "pgsql_tier" {
     name = "pgsql"
     service_delegation {
       name = "Microsoft.DBforPostgreSQL/flexibleServers"
+      actions = [
+        "Microsoft.Network/virtualNetworks/subnets/join/action",
+      ]
     }
   }
 }