Bug: Duplicate Email Check in User Registration

[iRahmanG]

Description

Duplicate emails are currently caught only when the database throws
DataIntegrityViolationException. This makes the code harder to read,
maintain, and extend.

Current Behavior

• User registers with an existing email.
• Save attempt triggers a database constraint error.
• Controller catches the error and returns a generic response.

Expected Behavior

• Service checks if email already exists before saving.
• If duplicate, throw a custom UserAlreadyExistsException.
• Global exception handler returns a clear, consistent API response.

Proposed Fix

• Add email check in AuthService.
• Create UserAlreadyExistsException.
• Handle it in GlobalExceptionHandler.
• Remove reliance on database errors for business logic.

Benefits

• Cleaner validation in service layer
• Consistent error handling
• Easier to maintain and extend

Files Affected

• AuthService.java
• AuthController.java
• UserRepository.java
• GlobalExceptionHandler.java
• UserAlreadyExistsException.java (new)

[iRahmanG]

/assign

[github-actions]

Hi @iRahmanG, this issue has been successfully assigned to you! 🎉

Make sure to read our Contributing Guidelines and submit your PR within the GSSoC timeframe. Happy coding! 🚀

[github-actions]

Hi @iRahmanG, this issue has been unassigned due to no activity/updates for 3 days. This keeps the repository active and open for other GSSoC contributors! Feel free to request it again if you are ready to submit a PR soon.