Network isolation validation

[robertvolkmann]

Validate network isolation configuration in a single location rather than performing validation in multiple places

[robertvolkmann]

@vknabel Do want to support empty RegistryMirrors or not?

gardener-extension-provider-metal/pkg/webhook/shoot/mutator.go

Line 170 in b38f4e8

if p.NetworkIsolation == nil || len(p.NetworkIsolation.RegistryMirrors) == 0 {

gardener-extension-provider-metal/pkg/webhook/controlplane/ensurer.go

Line 663 in b38f4e8

if len(mirrors) == 0 {

[vknabel]

@robertvolkmann if the network access type is not baseline, the NetworkIsolation and its RegistryMirrors must be set and contain at least one mirror.

[majst01]

rebase and run in test

[vknabel]

Worked fine in test