Ignore non-IPFS content paths in DNSLink records

[martinheidegger]

DNSLink currently returns the first non /dns-prefixed dnslink which means that per domain it is possible to use dnslink for only one "protocol". In order for dnslink to become useful for different decentralized protocols (hyper/dat, earthlink, etc.) it would need an option to specify a particular protocol to be looked for. Would you be open to a PR adding an option to this repo, defaulting to IPFS?

(Related issue on js-dnslink: here)

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[aschmahmann]

Yes, a PR would be welcome. However, the PR should go into go-namesys as that is the more used library for dnslink at the moment.

[martinheidegger]

@aschmahmann Probably somewhere here: https://github.com/ipfs/go-namesys/blob/2454122ef30efa1f4f86ffab33ea34b05eb848fe/dns.go#L171-L178, right?

[lidel]

@martinheidegger yes, we want to skip records where does not start with /ipns/ or /ipfs/ (right now it errors). Adding strings.HasPrefix check should do the trick.

We should also interpret /dnslink as /ipns and try to resolve it to the final form.