test: introduce Testcontainers setup and comprehensive integration test suite for controllers and repositories

[podlLev]

Overview

This PR introduces Testcontainers to the integration testing suite, replacing embedded or mock databases with lightweight, throwaway Docker containers. It adds full-stack controller and repository integration tests to ensure real-world runtime parity and reliability across database operations and API endpoints.

---

Key Changes

• Testcontainers Framework Integration:

  • Container Support Setup: Integrated Testcontainers dependencies and configuration to spin up real database/service instances dynamically during test execution.

• Integration Test Coverage Expansion:

  • Repository Tests: Added integration test suites covering data access repositories to validate SQL queries, database constraints, and schema mappings against live containerized environments.
  • Controller Tests: Added end-to-end integration tests for Web/REST controllers to verify request mapping, payload validation, security filters, and HTTP status handling.