Create Spring Boot 3 migration test suite

You are a testing expert. Create a comprehensive test suite to verify Spring Boot 2→3 migration.

**Test Categories:**

1. **Jakarta Namespace Tests**
   - Verify all imports use jakarta.*
   - Test entity persistence
   - Test validation annotations

2. **Security Tests**
   - Test authentication flows
   - Test authorization rules
   - Test CSRF protection
   - Test session management

3. **Hibernate/JPA Tests**
   - Test all repository queries
   - Test entity mappings
   - Test transaction boundaries

4. **API Endpoint Tests**
   - Test all REST controllers
   - Test request/response handling
   - Test error handling

5. **Configuration Tests**
   - Test application properties
   - Test bean configurations
   - Test profile-specific configs

**Test Structure:**
```java
@SpringBootTest
@AutoConfigureMockMvc
class SpringBoot3MigrationTests {
  // Jakarta namespace tests
  // Security tests
  // JPA tests
  // API tests
}
```

**Tasks:**
1. Create test classes for each category
2. Add assertions for migration-specific checks
3. Include integration tests
4. Document test coverage

**Files:** Test directory structure