BA-037 — Add durable user identity and uniqueness constraints

[MaryammAli]

• Type: Enhancement
• Affected area: src/users/, database entities
• BackendAcademy
• Summary: User preferences and profiles are keyed by arbitrary strings without a durable identity model.
• Acceptance criteria: User IDs, usernames, and email addresses have explicit formats and uniqueness rules; duplicate creation has stable errors.

[dev-RAM11]

@dev-RAM11 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi, I'd love to be assigned this issue. I've been actively contributing across Stellar Wave 4 through Wave 8 projects, working across smart contracts on Stellar/Soroban, Rust backends, NestJS APIs, Next.js frontends, and DevOps infrastructure — and I'm well-positioned to tackle this effectively.

I've reviewed the issue and have a clear implementation plan. I'll follow the project's contribution guidelines, write tests alongside the implementation, and keep the PR focused and reviewable.

Looking forward to contributing!

ℹ️ Repo Maintainers: To accept this application, review their application or assign @dev-RAM11 to this issue.

[anifast-123]

@anifast-123 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello maintainer, can i work on this issue?

ℹ️ Repo Maintainers: To accept this application, review their application or assign @anifast-123 to this issue.

[toroabduljalalyakubu]

@toroabduljalalyakubu has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello, I would like to work on this Issue. Thank you.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @toroabduljalalyakubu to this issue.

[drips-wave]

Congratulations, @toroabduljalalyakubu! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @toroabduljalalyakubu: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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[drips-wave]

This issue has been completed by @toroabduljalalyakubu as part of the Stellar Wave Program's 8th Wave 🥳

😎 @toroabduljalalyakubu: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here. You can also Leave a review to share your experience working on this issue.

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