Create API error code reference

[ayshadogo]

User Story:
As a frontend developer, I want a reference of all custom error codes so that I can display user-friendly messages.

Acceptance Criteria:

• /docs/errors.md documents all custom error codes
• Format: { code, httpStatus, message, description }
• Example: WALLET_SIGNATURE_INVALID, CAMPAIGN_NOT_FOUND, MILESTONE_NOT_UNLOCKED
• Error codes used consistently across all services

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[Michael997glitch]

@Michael997glitch has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi, I’m a smart contractor and a full-stack web developer, I have read through the issue and it’s something I’m capable of doing. Please assign me this work.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Michael997glitch to this issue.

[GreatShinro]

@GreatShinro has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi, can I work on this issue please?

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

[amosleoamadi]

@amosleoamadi has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Can i work on this please?

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

[AbdulSnk]

@AbdulSnk has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello,

I would like to apply to contribute to this issue. I have experience with JavaScript/TypeScript and backend development using NestJS and relational databases. I enjoy understanding requirements, writing clean and maintainable code, and collaborating through code reviews.

I have reviewed the issue description and would appreciate the opportunity to work on it. I am committed to communicating progress clearly and delivering a quality solution.

Thank you for your consideration.

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

[drips-wave]

Congratulations, @AbdulSnk! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @AbdulSnk: 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.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊

[grantfox-oss]

🦊 GrantFox — @AbdulSnk has been assigned to this issue!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #340)
2. Your PR will be reviewed by the Dfunder maintainers

Good luck! Track your progress on GrantFox.