Support IPNS PubSub

[eth-limo]

We would love to see full IPNS PubSub support in Rainbow. Currently most users leverage the DHT, however there are a handful of power users experimenting with novel use cases that rely upon PubSub. Currently the recommended way to enable PubSub is by configuring the RAINBOW_HTTP_ROUTERS setting to a /routing/v1 endpoint on Kubo, which is less than desirable.

[lidel]

Triage notes:

• @eth-limo mind elaborating why delegating routing is "less desirable"? operational complexity?
• we've discussed internally and PubSub is expensive, so would have to be opt-in. perhaps this should live outside of rainbow after all? the focus of rainbow is on retrieval and not routing?
  • someguy is the discreet tool we use as caching proxy to routing systems (IPNI, Amino DHT, IPNI)
    • https://specs.ipfs.tech/routing/http-routing-v1/#get-routing-v1-ipns-name

This way you dont need to run Kubo, just fleet of rainbows + someguy that acts as cachign proxy for routing.

[eth-limo]

Triage notes:

* [@eth-limo](https://github.com/eth-limo)  mind elaborating why delegating routing is "less desirable"?  operational complexity?

* we've discussed internally and PubSub is expensive, so would have to be opt-in. perhaps this should live outside of rainbow after all? the focus of rainbow is on retrieval and not routing?
  
  * [someguy](https://github.com/ipfs/someguy) is the discreet tool we use as caching proxy to routing systems (IPNI, Amino DHT, IPNI)
    
    * https://specs.ipfs.tech/routing/http-routing-v1/#get-routing-v1-ipns-name

This way you dont need to run Kubo, just fleet of rainbows + someguy that acts as cachign proxy for routing.

Yep it's mainly around operational complexity/costs. If someguy is all that's needed, then that should be an acceptable tradeoff.