feat: implement CreateDiaryService and usecase

src/main/kotlin/me/daegyeo/maru/diary/application/port/in/CreateDiaryUseCase.kt

@@ -0,0 +1,8 @@
+package me.daegyeo.maru.diary.application.port.`in`
+
+import me.daegyeo.maru.diary.application.domain.Diary
+import me.daegyeo.maru.diary.application.port.`in`.command.CreateDiaryCommand
+
+fun interface CreateDiaryUseCase {
+    fun createDiary(input: CreateDiaryCommand): Diary
+}

src/main/kotlin/me/daegyeo/maru/diary/application/port/in/command/CreateDiaryCommand.kt

@@ -0,0 +1,8 @@
+package me.daegyeo.maru.diary.application.port.`in`.command
+
+import java.util.UUID
+
+data class CreateDiaryCommand(
+    val content: String,
+    val userId: UUID,
+)

src/main/kotlin/me/daegyeo/maru/diary/application/service/CreateDiaryService.kt

@@ -0,0 +1,36 @@
+package me.daegyeo.maru.diary.application.service
+
+import me.daegyeo.maru.diary.application.domain.Diary
+import me.daegyeo.maru.diary.application.port.`in`.CreateDiaryUseCase
+import me.daegyeo.maru.diary.application.port.`in`.EncryptDiaryUseCase
+import me.daegyeo.maru.diary.application.port.`in`.command.CreateDiaryCommand
+import me.daegyeo.maru.diary.application.port.out.CreateDiaryPort
+import me.daegyeo.maru.diary.application.port.out.dto.CreateDiaryDto
+import me.daegyeo.maru.user.application.port.`in`.GetUserUseCase
+import org.springframework.stereotype.Service
+import org.springframework.transaction.annotation.Transactional
+
+@Service
+class CreateDiaryService(
+    private val getUserUseCase: GetUserUseCase,
+    private val createDiaryPort: CreateDiaryPort,
+    private val encryptDiaryUseCase: EncryptDiaryUseCase,
+) :
+    CreateDiaryUseCase {
+    @Transactional
+    override fun createDiary(input: CreateDiaryCommand): Diary {
+        val user = getUserUseCase.getUser(input.userId)
+        val encryptedContent = encryptDiaryUseCase.encryptDiary(input.content)
+        val diary =
+            createDiaryPort.createDiary(
+                CreateDiaryDto(
+                    userId = user.userId,
+                    content = encryptedContent,
+                ),
+            )
+        return diary.let {
+            it.content = ""
+            it
+        }
+    }
+}