feat: add payment processor for new transaction flow

[samfert]

Summary

Adds a new PaymentProcessor class to handle payment transactions with security best practices:

• SQL Injection Prevention: Uses PreparedStatement with parameterized queries
• Secure Credentials: Database credentials loaded from environment variables (DB_URL, DB_USER, DB_PASSWORD)
• Cryptographic Security: Uses SecureRandom for transaction ID generation and SHA-256 for hashing
• Resource Management: Implements try-with-resources for proper Connection and Statement cleanup
• Logging: Uses java.util.logging.Logger with lazy evaluation; masks card numbers in logs
• Null Safety: Validates account objects before dereferencing

SonarQube Quality Gate Status

Status: PASSING

All code quality conditions met:

• Coverage on New Code: 85% (threshold: 80%)
• Reliability Rating: A
• Security Rating: A
• Maintainability Rating: A
• Security Hotspots Reviewed: 100%
• Duplicated Lines: 0%

Updates Since Last Revision

Added complete Maven build infrastructure and test coverage to resolve the quality gate:

1. Maven Module Setup (demo/pom.xml): Added JUnit 5, Mockito, and JaCoCo for test coverage reporting
2. Test Suites: Added comprehensive unit tests for PaymentProcessor and VulnerableCode classes (~45 test cases)
3. CI Integration: Updated workflow to build demo module and generate JaCoCo coverage reports
4. SonarQube Config: Updated sonar-project.properties to properly configure sources, tests, and coverage paths

Review & Testing Checklist for Human

• Verify database connectivity: Set environment variables (DB_URL, DB_USER, DB_PASSWORD) and test processPayment() against a real/test database - unit tests only verify SQLException is thrown when DB unavailable
• Review default empty password: DB_PASSWORD defaults to empty string when env var not set - verify this is acceptable for your deployment
• Confirm package structure: Files are in demo/ folder with package demo; - verify this is the intended location vs. standard com.banking.demo structure

Test Plan

1. Set environment variables: DB_URL, DB_USER, DB_PASSWORD
2. Create a test database with a payments table containing account_id, amount, description columns
3. Call processPayment() and verify record is inserted
4. Call generateTransactionId() multiple times and verify unique IDs
5. Call logPayment() and verify card numbers are masked in output

Notes

• Unit tests achieve 85% coverage but do not test actual database operations (no integration tests)
• All tests pass locally and in CI

Link to Devin runs:

• https://app.devin.ai/sessions/9b2624b85af54579adb8322c15facaed
• https://app.devin.ai/sessions/27336fef59a94e808559260c6f57ba47
• https://app.devin.ai/sessions/3cb65bee8d5e4c42844f92bcf8722a3b

Requested by: Sam Fertig (sam.fertig@cognition.ai) (@samfert-codeium)

[github-actions]

🤖 Devin AI Quality Gate Remediation Triggered

A SonarQube Quality Gate Remediation Specialist (Devin AI) has been assigned to fix all quality gate failures.

📊 Quality Gate Analysis

• Total Issues: 7
• Vulnerabilities: 1 🔴
• Bugs: 3 🐛
• Code Smells: 3 💨
• Security Hotspots: 0 🔥

🔗 Links

• 👀 Monitor Devin Session
• 📊 SonarQube Dashboard
• 🔧 GitHub Actions Run

---

Note: Devin will push a fix to this branch. The workflow will automatically re-run to validate.

[github-actions]

🤖 Devin AI Quality Gate Remediation Triggered

A SonarQube Quality Gate Remediation Specialist (Devin AI) has been assigned to fix all quality gate failures.

📊 Quality Gate Analysis

• Total Issues: 7
• Vulnerabilities: 1 🔴
• Bugs: 3 🐛
• Code Smells: 3 💨
• Security Hotspots: 0 🔥

🔗 Links

• 👀 Monitor Devin Session
• 📊 SonarQube Dashboard
• 🔧 GitHub Actions Run

---

Note: Devin will push a fix to this branch. The workflow will automatically re-run to validate.

[github-actions]

🤖 Devin AI Quality Gate Remediation Triggered

A SonarQube Quality Gate Remediation Specialist (Devin AI) has been assigned to fix all quality gate failures.

📊 Quality Gate Analysis

• Total Issues: 7
• Vulnerabilities: 1 🔴
• Bugs: 3 🐛
• Code Smells: 3 💨
• Security Hotspots: 0 🔥

🔗 Links

• 👀 Monitor Devin Session
• 📊 SonarQube Dashboard
• 🔧 GitHub Actions Run

---

Note: Devin will push a fix to this branch. The workflow will automatically re-run to validate.

[sonarqubecloud]

Quality Gate passed

Issues
6 New issues
0 Accepted issues

Measures
0 Security Hotspots
85.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud