fix(json): применять Kotlin-модуль Jackson 3

services/identity-service/src/main/kotlin/ru/ysu/lms/identity/config/JacksonConfig.kt

@@ -0,0 +1,20 @@
+package ru.ysu.lms.identity.config
+
+import org.springframework.boot.jackson.autoconfigure.JsonMapperBuilderCustomizer
+import org.springframework.context.annotation.Bean
+import org.springframework.context.annotation.Configuration
+import tools.jackson.module.kotlin.KotlinModule
+
+/**
+ * Jackson 3 не подхватывает Kotlin-модуль автоматически в Spring Boot 4:
+ * без него DTO с default-значениями требуют все поля в JSON.
+ */
+@Configuration
+class JacksonConfig {
+    @Bean
+    fun kotlinModule(): KotlinModule = KotlinModule.Builder().build()
+
+    @Bean
+    fun kotlinJsonCustomizer(): JsonMapperBuilderCustomizer =
+        JsonMapperBuilderCustomizer { builder -> builder.addModule(KotlinModule.Builder().build()) }
+}

services/identity-service/src/test/kotlin/ru/ysu/lms/identity/roster/TeacherIntegrationTest.kt

@@ -65,6 +65,8 @@ class TeacherIntegrationTest {
 
     @Autowired lateinit var context: WebApplicationContext
 
+    @Autowired lateinit var jsonMapper: tools.jackson.databind.json.JsonMapper
+
     private val mockMvc: MockMvc by lazy {
         MockMvcBuilders
             .webAppContextSetup(context)
@@ -184,6 +186,19 @@ class TeacherIntegrationTest {
             }
     }
 
+    @Test
+    fun `student creation accepts omitted optional json fields`() {
+        val request =
+            jsonMapper.readValue(
+                """{"studentNo":"api-student-1","lastName":"Тестов"}""",
+                CreateStudentRequest::class.java,
+            )
+        assertEquals("api-student-1", request.studentNo)
+        assertEquals("Тестов", request.lastName)
+        assertEquals("", request.firstName)
+        assertEquals("", request.basis)
+    }
+
     private fun student(login: String): Account =
         Account(
             login = login,