feat: 絵文字のエンティティとRepositoryを追加

src/main/kotlin/dev/usbharu/hideout/core/domain/model/emoji/CustomEmoji.kt

@@ -0,0 +1,24 @@
+package dev.usbharu.hideout.core.domain.model.emoji
+
+import java.time.Instant
+
+sealed class Emoji {
+    abstract val domain: String
+    abstract val name: String
+}
+
+data class CustomEmoji(
+    val id: Long,
+    override val name: String,
+    override val domain: String,
+    val instanceId: Long,
+    val url: String,
+    val category: String,
+    val createdAt: Instant
+) : Emoji()
+
+data class UnicodeEmoji(
+    override val name: String
+) : Emoji() {
+    override val domain: String = "unicode.org"
+}

src/main/kotlin/dev/usbharu/hideout/core/domain/model/emoji/CustomEmojiRepository.kt

@@ -0,0 +1,7 @@
+package dev.usbharu.hideout.core.domain.model.emoji
+
+interface CustomEmojiRepository {
+    suspend fun save(customEmoji: CustomEmoji): CustomEmoji
+    suspend fun findById(id: Long): CustomEmoji?
+    suspend fun delete(customEmoji: CustomEmoji)
+}