Hi,
got an error by executing your code:
╷
│ Error: API Error Creating Resource Subaccount
│
│ with btp_subaccount.project_subaccount,
│ on main.tf line 1, in resource “btp_subaccount” “project_subaccount”:
│ 1: resource “btp_subaccount” “project_subaccount” {
│
│ Subdomain dev-project-abc already exists in the current region [Error: 20007/409]
solved this by changing subdomain value.