fix(agent-assignment): 소속 시각 UTC 변환을 적용한다

src/test/kotlin/kr/co/vividnext/sodalive/extensions/LocalDateTimeExtensionsTest.kt

@@ -0,0 +1,37 @@
+package kr.co.vividnext.sodalive.extensions
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.fail
+import org.junit.jupiter.api.Test
+import java.time.LocalDateTime
+import java.time.ZoneId
+
+class LocalDateTimeExtensionsTest {
+    @Test
+    fun shouldConvertToUtcUsingKstByDefault() {
+        val localDateTime = LocalDateTime.of(2026, 4, 9, 10, 0)
+
+        val utcDateTime = invokeConvertToUtc(localDateTime)
+
+        assertEquals(LocalDateTime.of(2026, 4, 9, 1, 0), utcDateTime)
+    }
+
+    @Test
+    fun shouldConvertToUtcUsingProvidedTimezone() {
+        val localDateTime = LocalDateTime.of(2026, 4, 9, 10, 0)
+
+        val utcDateTime = invokeConvertToUtc(localDateTime, ZoneId.of("Asia/Bangkok"))
+
+        assertEquals(LocalDateTime.of(2026, 4, 9, 3, 0), utcDateTime)
+    }
+
+    private fun invokeConvertToUtc(localDateTime: LocalDateTime, timeZone: ZoneId = ZoneId.of("Asia/Seoul")): LocalDateTime {
+        return try {
+            val method = Class.forName("kr.co.vividnext.sodalive.extensions.LocalDateTimeExtensionsKt")
+                .getMethod("convertToUtc", LocalDateTime::class.java, ZoneId::class.java)
+            method.invoke(null, localDateTime, timeZone) as LocalDateTime
+        } catch (e: ReflectiveOperationException) {
+            fail("LocalDateTime.convertToUtc 확장함수를 찾을 수 없습니다.")
+        }
+    }
+}