Enhance DIGIPIN API with full input validation, improved error handling, and middleware upgrades

[Rajdip585]

Overview

This pull request introduces a set of improvements to the DIGIPIN API, focusing on input validation, error handling, and safer request processing.
The goal is to make the API more robust, predictable, and user-friendly while maintaining backward compatibility.

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Key Improvements

1. Added Comprehensive Input Validation

• Validates latitude, longitude, and digipin fields for:
  • Missing values
  • Incorrect types
  • Invalid number formats
  • Empty strings
• Introduced helper functions:
  • isValidNumber()
  • isValidString()

2. Improved Error Handling

• Added structured error responses with explicit error codes.
• Better handling of malformed JSON payloads.
• Clear error messaging for invalid inputs in both POST and GET endpoints.

3. Middleware Enhancements

• Added a validateJsonContentType middleware to enforce application/json for POST requests.
• Improved JSON parsing error handler (invalid/malformed JSON now returns a clear 400 response).

4. Route-Level Improvements

• Rewrote DIGIPIN encode/decode routes for clarity, safety, and maintainability.
• Consistent parsing of query parameters and body data.
• Clean separation of validation, parsing, and execution logic.

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Files Updated

• src/app.js
• src/routes/digipin.routes.js
• server.js

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Why These Changes Matter

• Prevents server crashes or unpredictable behavior caused by invalid inputs.
• Guarantees consistent API responses across clients (mobile, web).
• Makes the API more production-ready with clearer contracts and stricter validation.
• Improves developer experience and debugging reliability.

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Compatibility

✔ No breaking changes to the API structure
✔ Existing clients continue to work
✔ New validations only reject invalid data (expected behavior)

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Request

Please review the changes and merge if they align with the project's direction.
I am open to adjustments or suggestions to align with your preferred coding style or architecture.

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Thank you!