OVHcloud customers using 'ovh' provider for large DNS zone will spend a
lot of time waiting for all records to be retrieved from the API. As
records can't change without a modification of the SOA Serial of the DNS
zone, this commit adds a client-side cache that stores the value of the
DNS records for each zone, based of the current SOA Serial value of the
zone. In case the SOA Serial of the zone is identical to the one in
cache, we can serve all the records directly from cache. Otherwise,
fallback on refreshing the cache from the API.
Signed-off-by: Romain Beuque <556072+rbeuque74@users.noreply.github.com>
