Add optional Pubsub.SeenMessagesTTL to Kubo config

[smrz2001]

Checklist

• My issue is specific & actionable.
• I am not suggesting a protocol enhancement.
• I have searched on the issue tracker for my issue.

Description

As discussed in this Slack thread, this is a feature request to make Pubsub.SeenMessagesTTL configurable in Kubo's Pubsub config:

• Kubo uses https://github.com/libp2p/go-libp2p-pubsub/ which has default TimeCacheDuration set to 120 seconds. This is how long it will remember "already seen message IDs".
  • This is the same as in JS implementation (which was bumberd from 30s to 2m to match GO)
    There is no configuration option in Kubo to increase this duration atm, but we could expose one in future version (we release ~every 5 weeks)
  • go-libp2p-pubsub supports custom initialization via WithSeenMessagesTTL but it is not wired up in Kubo's config yet
  • If you find this useful, please open feature request to add optional Pubsub.SeenMessagesTTL to Kubo's config (https://github.com/ipfs/kubo/issues/)

Support for this option is now available in go-libp2p-pubsub v0.7.0 onwards.

As explained in that thread, we would very much like to be able to use this option to adjust the duration for which pubsub messages can remain active on the network.

[lidel]

Exposing this as optionalDuration in the config sounds sensible.

If someone wants this feature and is willing to submit a PR, we are happy to review.