Add ENR Record.init and update call for dual stack

[kdeme]

Attempt to add dual stack support in ENR in line with the current API.
In draft however as I don't really like this API, it feels rather clumsy, both in implementation and in usage.

I'll probably implement dualstack in Fluffy to see how it would typically be used, and continue/adjust from there.

Might also go for some EnrBuilder approach instead to get to something in the trend of:

let enr = EnrBuilder.init().tcp4(Port(9000)).ip4(ip4).ip6(ip6).build(privatekey)

and

let enrUpdated = EnrBuilder.init(enr).tcp4(Port(9000)).ip4(ip4).build(privatekey)

Ideas and/or use cases are welcome.

[kdeme]

There is no Opt here, as in dual stack case I'm assuming both IPs or no IP is known (perhaps this is not correct?).

Also not using IpAddress as from that type I cannot be sure whether it is IPv4 or IPv6 (unless I check for it of course).

In the other use cases, the init call with only 1 address can be used.

[kdeme]

Perhaps I don't need to do this check and can let the user decide what they want to do in case of same ports.

[kdeme]

Perhaps it makes more sense to unset the field in that case

[kdeme]

The fact that I have to write such a lengthy documentation for this call probably is not a sign of good API.

[NagyZoltanPeter]

Attempt to add dual stack support in ENR in line with the current API. In draft however as I don't really like this API, it feels rather clumsy, both in implementation and in usage.

I'll probably implement dualstack in Fluffy to see how it would typically be used, and continue/adjust from there.

Might also go for some EnrBuilder approach instead to get to something in the trend of:

let enr = EnrBuilder.init().tcp4(Port(9000)).ip4(ip4).ip6(ip6).build(privatekey)

and

let enrUpdated = EnrBuilder.init(enr).tcp4(Port(9000)).ip4(ip4).build(privatekey)

Ideas and/or use cases are welcome.

@kdeme
Thanks for the effort! From Waku point of view I have gone through it.
From our POV I would really vote for the builder pattern than anything else. In Waku we have something similar implemented over enr.Record. But the approach you crafter here, above it might be even better.
I think it has greater advantages controlling what can get into the ENR or filtering duplicates, fine graining updates (with Opt.none for clearing a field).

For the draft solution, I have the feeling that making IP4 and IP6 mandatory we will still end up in incompatibilities/regression. Do you see dual stack to be forced?

[arnetheduck]

Do you see dual stack to be forced?

re ipv6, the idea in general is to push towards a world where dual stack is enabled by default (if the platform allows it), ie if the caller or user does "nothing special", they should end up in a dual stack world that serves both ipv4 and ipv6.