GCP Egress firenet provisioning failed due to error "local.lan_vpc is null"

[danielzh9]

The module is trying to find "lan_vpc" info in transit_module.mc_firenet_details section:
lan_vpc = var.transit_module.mc_firenet_details.lan_vpc

but that section's lan_vpc is null.

instead, the lan_vpc info can be parsed from transit_gateway's section and the name is lan_vpc_id, not lan_vpc:
lan_vpc = var.transit_module.transit_gateway.lan_vpc_id