Bug: DevCard public URL returns 404 after username change

[Nareshkumawat-star]

Describe the bug

When a user changes their username, their old public DevCard URL (e.g. devcard.app/oldusername) returns a 404 instead of redirecting to the new URL. Any previously shared links or QR codes pointing to the old URL break permanently.

Steps to Reproduce

1. Create a DevCard with username alice
2. Share or embed the card URL
3. Change username to alice2
4. Visit the old URL — 404 error

Expected Behavior

The old username URL should 301 redirect to the new URL for at least 90 days.

Suggested Fix

Store previous usernames in a username_redirects table and add a redirect middleware that checks it before returning 404.

[github-actions]

Hi @Nareshkumawat-star,

Thanks for opening this issue.

Please reply with one of the following areas so the issue can be routed to the appropriate team member:

- /backend
- /web
- /mobile
- /devops

Once an area is selected, the corresponding label will be added automatically.

[Nareshkumawat-star]

/backend

[github-actions]

The issue has been classified as backend.

@Harxhit, please review and triage this issue when available.

The backend label has been applied and the issue has been routed accordingly.

[yachikadev]

I'd like to work on this. Here's my approach:
Schema: New username_redirects table — old_username (unique, indexed), current_user_id (FK to users), created_at. Indexing old_username keeps the lookup fast since it'll be hit on every 404 path.
Flow: On username change, before updating the user record, insert the old username into username_redirects pointing to the user's id. Add a check in the route/middleware layer — if old_username lookup fails in users, query username_redirects and 302-redirect to the current username (302 instead of 301 since it's a temporary mapping, not permanent — avoids browsers/CDNs caching it forever).
Edge case: if a redirected username later gets reclaimed by a different user during signup, that username_redirects row needs to be deleted/invalidated at that point — otherwise the old redirect would incorrectly point visitors to someone else's profile.
Testing: will add a test for the happy path (old → new redirect works), the reclaim case (redirect stops working once reclaimed), and a direct-404 case (username never existed).
Could I get this assigned to me?

[Harxhit]

@Nareshkumawat-star I have assigned this issue to you.