Add tests to support TTL

[martinheidegger]

The implementations should be forwarding the TTL for the txt entries returned by the server.

The API should probably look like:

{
  "links": {
    "ipfs": "QmTg....yomU"
  },
  "path": [],
  "log": [],
  "ttl": {
    "ipfs": 100
  }
}

This way the ttl can be optional, and users can choose if they implement ttl or not.

[lidel]

👍 as this is a must-have feature for production use (cc ipfs/kubo#8074 (review))

Is there is an edge case where more than one TXT record for /ipfs/ content path exist (eahc with different TTL) or are we returning CONFLICT_ENTRY error for that?

[martinheidegger]

If multiple TXT entries for the same key are returned it will use the higher one and put CONFLICT_ENTRY messages in the log for the others. The TTL for the returned entry would be the TTL of the returned TXT entry.

[martinheidegger]

Added in de471b9