ServiceCIDRs are protected by finalizers and the CIDRs fields are
inmutable once set, only the readiness state impact the allocator
as it can only allocate IPs if any of the ServiceCIDR is ready.
The Add/Update events triggers a reconcilation of the current state
of the ServiceCIDR present in the informers with the existing IP
allocators.
The Delete events are handled directly to update or delete the
corresponing IP allocator.
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