feat: add validation-service microservice

[devin-ai-integration]

feat: add validation-service microservice to centralize validation logic

Summary

Extracts validation logic from trade-service (validateTicker, validateAccount) and account-service (validatePerson) into a new validation-service microservice (port 18094). Both consuming services now delegate to validation-service via REST instead of calling downstream services directly.

New service: validation-service/ — Spring Boot 3.3.13, Java 21, exposes:

• GET /validate/ticker/{ticker} — validates against reference-data service
• GET /validate/account/{id} — validates against account-service
• GET /validate/person?username={username} — validates against people-service
• POST /validate/trade-order — combined ticker + account validation

Modified services:

• trade-service — removed validation methods, now calls /validate/trade-order
• account-service — removed validatePerson, now calls /validate/person

Infrastructure:

• docker-compose.yml — added validation-service container, updated service dependencies
• ingress/nginx.traderx.conf.template — added /validation-service/ proxy route
• docs/c4/c4-diagram.dsl — added validationService container and updated relationships

Tests:

• validation-service: unit tests for 3 service classes, integration test for controller (15 tests total)
• trade-service: controller test for validation flow (2 tests)

Builds pass: ./gradlew build succeeds for both validation-service and trade-service.

Local Testing Results

All 11 containers start successfully with docker-compose up --build, including the new validation-service on port 18094.

Validation-service endpoints verified via curl:

• GET /validate/ticker/AAPL → {"valid":true,"errors":[]}
• GET /validate/ticker/INVALID_TICKER → {"valid":false,"errors":["INVALID_TICKER not found in Reference data service."]}
• POST /validate/trade-order with both invalid ticker and account → collects all errors correctly
• Ingress proxy at localhost:8080/validation-service/ routes correctly to validation-service

Swagger UI loads at http://localhost:18094/swagger-ui.html:

Recording of local testing session:

View original video (rec-d26ddedea55c4d329844ce742563c229-edited.mp4)

Note: The Angular frontend has a pre-existing build error (TS2345 in assign-user.component.ts) unrelated to this PR. All backend services start and function correctly.

Review & Testing Checklist for Human

⚠️ Risk Level: Yellow — Extraction is straightforward and local testing passed, but there are runtime edge cases not covered by automated tests.

• Check TradeOrderController NPE risk — TradeOrderController.java line ~50: if restTemplate.postForObject() returns null, validationResult.getErrors() will NPE in the else branch. Should add null-safe handling.
• Verify error handling when validation-service is down — Both TradeOrderController and AccountUserController make REST calls to validation-service with no try-catch. If validation-service is unreachable, unhandled RestClientException → 500 error. Consider adding resilience (circuit breaker, fallback, or graceful error).
• AccountUserController uses raw Map<?, ?> for validation result — Instead of a typed DTO like trade-service's ValidationResult, account-service deserializes the response as Map.class. This is fragile—consider adding a ValidationResult DTO to account-service as well.
• End-to-end trade execution not tested — Validation-service endpoints were tested directly via curl, but a full trade submission through trade-service → validation-service → reference-data/account-service was not verified. Recommend testing this flow manually.

Recommended Test Plan

1. ✅ Start stack: docker-compose up (verified—all services start)
2. ✅ Test validation-service endpoints directly via curl (verified—all return correct responses)
3. ⚠️ Still needed: Create a trade via trade-service with valid ticker + valid account → should succeed
4. ⚠️ Still needed: Create a trade with invalid ticker → should fail with validation error from validation-service
5. ⚠️ Still needed: Create an account user with valid username → should succeed via validation-service
6. ⚠️ Still needed: Shut down validation-service, attempt trade → verify error handling behavior

Notes

• Link to Devin Session: https://app.devin.ai/sessions/f9762bc1c9e4464da67eeff5a5b145fb
• Requested by: @mbatchelor81
• CI checks passed: Snyk security & license scans ✅
• (Minor) Test pattern inconsistency: PersonValidationServiceTest uses MockRestServiceServer while TickerValidationServiceTest and AccountValidationServiceTest use @Mock/@InjectMocks. All build/pass but worth standardizing in future refactoring.

[devin-ai-integration]

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