Fix Cody onboarding redirect problem

[vdavid]

Closes https://linear.app/sourcegraph/issue/PRIME-299/unable-to-sign-into-cody-account-via-github

The problem is that in some cases, the Cody Management page (https://courcegraph.com/cody/manage) doesn't redirect requests to the returnTo URL passed to it.
The situation when this occurs is when the user has not completed the Cody onboarding flow in the browser they are seeing the page.

History of the bug:

• Originally, it worked, but only because of an apparently accidental, transient state in this line where the variable completed was initialized with the value of true.
• I made a change in December (in https://github.com/sourcegraph/sourcegraph/pull/58854) where I removed that transient state, but thus, I broke the redirect, which caused severe onboarding UX problems.
• This PR fixes the redirect again, by making the redirect decision logic consider requestFrom=CODY even in the return URL.

This is actually just another hack; the right solution would be for clients to propoerly pass the request=CODY to the Cody Management page itself, not just in the return URL. But it is what it is, this solution works with that glitch, which is a solution that works with versions of clients that are already released.

Test plan

I've tested locally with all combinations of

• ab-shortened-install-first-signup-flow-cody-2024-04 feature flag being on/off
• the string requestFrom=CODY present/not present in the return URL
• the cody.onboarding.completed temporary setting being true/false

Changelog

fix(cody): redirect Cody client requests to the access token creation page in all cases

[olafurpg]

I think this fix will only work for VS Code

[olafurpg]

I just double-checked that the returnTo parameter is decoded in the URL https://sourcegraph.com/cody/manage?returnTo=%2Fuser%2Fsettings%2Ftokens%2Fnew%2Fcallback%3FrequestFrom%3DCODY%26tokenReceiverUrl%3Dhttp%253A%252F%252F127.0.0.1%253A59233%252F0cd3184fa6ced459885cefd00be0036d

However, this fix doesn't work for JetBrains which has requestFrom=JETBRAINS-$PORT_NUMBER. Example URL

https://sourcegraph.com/cody/manage?returnTo=%2Fuser%2Fsettings%2Ftokens%2Fnew%2Fcallback%3FrequestFrom%3DJETBRAINS-63342

[vdavid]

@olafurpg I see. Looks like a miscommunication happened about the intended interface of this page, as none of the clients seem to be passing the requestFrom=CODY argument to the /cody/manage page specifically. I think this requirement might not have been communicated to client teams. Anyway, it is what it is, let's figure out how to go forward.

I have a few ideas for a solution:
a.) Add yet another exception to detect requestFrom=JETBRAINS in the URL. But then, Neovim or others might fall into the same hole.
b.) Detect "/user/settings/tokens/new/callback" in the URL instead—all clients use it, so it clearly indicates a call coming from Cody.
c.) I wonder if we could just do the redirect for any returnTo without showing the onboarding form. I'd need to check with Product, but as I'm aware of our flows, we don't call this page with a returnTo with the intention for the user to go through the onboarding flow and then be redirected.

If Product agrees, I'd just go with c.), as that's the simplest logic.

[olafurpg]

We will add login flows for Visual Studio and Eclipse soon. I vote for c), but option b) also works

[vdavid]

@olafurpg, I've implemented a solution between b and c, redirecting all requests that have requestFrom as a search param to /cody/manage, or anywhere in the returnTo URL: https://github.com/sourcegraph/sourcegraph/pull/63096/commits/2421f60d89c848e1302d7a17316090744042c06c

[olafurpg]

Thank you!