feat: support redirects for UnixFS directories

achingbrain commented 8 months ago

Adds support for simulating redirects for UnixFS directories.

We're somewhat in uncharted water here because window.fetch does this transparently unless you specify a redirect option, none of which actually allow you to manually follow a redirect.

The states we can be in are:

URL: ipfs://QmFoo/dir/
- Happy path
- 200 response
- response.redirected = false
- response.url = 'ipfs://QmFoo/dir'

2: URL: ipfs://QmFoo/dir, redirect: 'follow'

The default value
Simulates automatically following a redirect
200 response
response.redirected = true
response.url = 'ipfs://QmFoo/dir/'

3: URL: ipfs://QmFoo/dir, redirect: 'error'

Throw an error if a redirect would take place
Throws TypeError('Failed to Fetch') same as window.fetch

4: URL: ipfs://QmFoo/dir, redirect: 'manual'

Allows a caller to take action on the redirect
301 response
response.redirected = false
response.url = 'ipfs://QmFoo/dir
response.headers.get('location') = 'ipfs://QmFoo/dir/'

Number 4 is the furthest from the fetch spec but to follow the spec would make it impossible to actually follow a redirect.

Refs: https://github.com/ipfs-shipyard/helia-service-worker-gateway/issues/62

Change checklist

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