refactor: remove unused helia, use verified fetch, and simplify code

[2color]

PR Summary

This PR is mostly refactoring with some small changes to make it easier to implement caching.

• Replace the singleton helia instance in favour of a verifiedFetch instance because the helia instance wasn't actually used
• Remove the indexedDB block store - this is a temporary measure until I decide how to implement the cache in Cache final Responses #73. Since the helia instance wasn't used and verifiedFetch was instantiated on every request, this has no effect
• Simplify the heliaFetch function and break it into more easily testable functions
• Move the default routers and gateways config to storage so that the user can also customise the default config (not finished since it's initially loaded from localStorage which can probably removed as per discussion)
• Fixes Slow iframe requests to root domain (unintended cache bypass) #88 by loading the config page using a hash fragment instead of query param

Notes & open questions

• We may still want to use indexedDB blockstore for caching (related Cache final Responses #73) . If so, see fix!: move dnsResolvers to options helia-verified-fetch#13 which should enable us to use it while customising the DoH endpoints.
• Config passing between origins needs to be more carefully tested. It seems like in some cases this is not working properly, e.g. when auto-reload is set up and there isn't enough time for the message to be passed from the root to the subdomain origin.

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if necessary (this includes comments as well)
• I have added tests that prove my fix is effective or that my feature works

[SgtPooki]

A few comments before I review:

Replace the singleton helia instance in favour of a verifiedFetch instance because the helia instance wasn't actually used

👍 great, yea this needed done!

Move the default routers and gateways config to storage so that the user can also customise the default config (not finished since it's initially loaded from localStorage which can probably removed #86 (comment))

moved them to which storage if we removed indexedDB? nvm, i see that they're moved to localStorage.

Move the default routers and gateways config to storage so that the user can also customise the default config (not finished since it's initially loaded from localStorage which can probably removed #86 (comment))

I believe in the last helia WG call we discussed not removing localStorage.

We may still want to use indexedDB blockstore for caching (related #73) . If so, see ipfs/helia-verified-fetch#13 which should enable us to use it while customising the DoH endpoints.

We do still want to use indexedDB for passing data to and from the config page. I don't think we need the indexedDB blockstore at all. A plain indexedDB instance should work

Config passing between origins needs to be more carefully tested. It seems like in some cases this is not working properly, e.g. when auto-reload is set up and there isn't enough time for the message to be passed from the root to the subdomain origin.

There is a TODO to use the commsChannel to use passMessageAndWaitForResponse (or whatever its called) which would require waiting until the message is passed and sw responds back

[SgtPooki]

I'm a fan of these changes in general. I think there are a few changes we should get in before merging though.

Thanks Daniel!

[SgtPooki]

Suggested change

	return new Response('heliaFetch error: ' + errorMessage, { status: 500 })
	return new Response('verifiedFetch error: ' + errorMessage, { status: 500 })