Rewrite gateway4/gateway6 to routes to satisfy Debian Bookworm

build/default/hvn0.lab.ipng.ch/vpp0-0/etc/netplan/01-netcfg.yaml

@@ -8,5 +8,8 @@ network:
       dhcp4: false
       mtu: 9000
       addresses: [ 198.19.5.16/27, 2001:678:d78:50b::10/64 ]
-      gateway4: 198.19.5.1
-      gateway6: 2001:678:d78:50b::1
+      routes:
+       - to: 0.0.0.0/0
+         via: 198.19.5.1
+       - to: ::/0
+         via: 2001:678:d78:50b::1

build/default/hvn0.lab.ipng.ch/vpp0-1/etc/netplan/01-netcfg.yaml

@@ -8,5 +8,8 @@ network:
       dhcp4: false
       mtu: 9000
       addresses: [ 198.19.5.17/27, 2001:678:d78:50b::11/64 ]
-      gateway4: 198.19.5.1
-      gateway6: 2001:678:d78:50b::1
+      routes:
+       - to: 0.0.0.0/0
+         via: 198.19.5.1
+       - to: ::/0
+         via: 2001:678:d78:50b::1

build/default/hvn0.lab.ipng.ch/vpp0-2/etc/netplan/01-netcfg.yaml

@@ -8,5 +8,8 @@ network:
       dhcp4: false
       mtu: 9000
       addresses: [ 198.19.5.18/27, 2001:678:d78:50b::12/64 ]
-      gateway4: 198.19.5.1
-      gateway6: 2001:678:d78:50b::1
+      routes:
+       - to: 0.0.0.0/0
+         via: 198.19.5.1
+       - to: ::/0
+         via: 2001:678:d78:50b::1

build/default/hvn0.lab.ipng.ch/vpp0-3/etc/netplan/01-netcfg.yaml

@@ -8,5 +8,8 @@ network:
       dhcp4: false
       mtu: 9000
       addresses: [ 198.19.5.19/27, 2001:678:d78:50b::13/64 ]
-      gateway4: 198.19.5.1
-      gateway6: 2001:678:d78:50b::1
+      routes:
+       - to: 0.0.0.0/0
+         via: 198.19.5.1
+       - to: ::/0
+         via: 2001:678:d78:50b::1

overlays/bird/common/etc/netplan/01-netcfg.yaml.j2

@@ -8,6 +8,9 @@ network:
       dhcp4: false
       mtu: 9000
       addresses: [ {{node.mgmt.ipv4}}, {{node.mgmt.ipv6}} ]
-      gateway4: {{lab.mgmt.gw4}}
-      gateway6: {{lab.mgmt.gw6}}
+      routes:
+       - to: 0.0.0.0/0
+         via: {{lab.mgmt.gw4}}
+       - to: ::/0
+         via: {{lab.mgmt.gw6}}