Add `Routing.Type=delegated` to only use `Routing.DelegatedRouters`

[lidel]

Problem / User need

Right now (0.35) there is no easy way to disable Amino DHT AND only use Routing.DelegatedRouters.

This setup was requested by users (example), and allows them to turn off DHT client on Kubo and delegate it to a self-hosted instance of Someguy that exposes /routing/v1 caching proxy to Amino DHT and any other Delegated routing endpoints.

Implementation ideas

Since it is already possible to turn off routing with Routing.Type=none, we could add Routing.Type=delegated which would work the same way as Routing.Type=autoclient but without initializing Amino DHT client, and only initializing Delegated routers from Routing.DelegatedRouters

Caveats

• Error if Provider and Reprovider is enabled, asking user to explciitly disable them, so user knows they are read-only client and dont provide anything?
• There is no Spec for Delegated Provides over HTTP. ipfs daemon must print a loud warning informing user that node running with Routing.Type=delegated will not be able to provide data on Amino DHT. Prior art:
  

  kubo/cmd/ipfs/kubo/daemon.go

  Lines 637 to 639 in 78ef5e9

  	⚠️ Provide and Reprovide systems are disabled due to 'Provide.Enabled=false'
  	⚠️ Local CIDs will not be announced to Amino DHT, making them impossible to retrieve without manual peering
  	⚠️ If this is not intentional, call 'ipfs config profile apply announce-on' or set Provide.Enabled=true'

[guillaumemichel]

Related to #10097. We could add a noop provide system for Routing.Type=delegated.

[KapilSareen]

I would like to take this up!

[KapilSareen]

Hi @lidel! I just opened the PR aiming to solve this issue. I'm new to the IPFS space and contributing as a way to learn more about the project and its internals. Please let me know if I'm misunderstanding anything or if there's a better approach, I’m happy to iterate and improve the changes based on your feedback.

[lidel]

Thank you for contribution, we may need to park this and #10874 until #10883 lands.