If no NS records for subdomain, check parent domain for NS records in header

[MattIPv4]

trafficstars

Tool relating to this issue

DNS

Feature request

Feature description

In the header currently, we show if the domain is using DO DNS or not. (https://github.com/do-community/dns-tool/blob/master/src/dns-lookup/templates/dodns.vue)

Eg:

However, if you search a subdomain that does not have any NS records, you get a rather unhelpful and potentially misleading message:

In this situation (subdomain with no NS), we should check the parent (sub)domain for NS records. We should loop until we either find an NS record, or we reach the root domain (in which case something has probably gone wrong as there must be an NS record somewhere, right?).

How the feature is useful

Allows the NS status (DO or not DO) to be conveyed even when looking up a subdomain.