Added the classes UniqueGiftModel, UniqueGiftSymbol, UniqueGiftBackdropColors, and UniqueGiftBackdrop to describe the properties of a unique gift.

Author: mircoianese

library/src/main/java/com/pengrad/telegrambot/model/gift/unique/UniqueGiftBackdrop.kt

@@ -0,0 +1,7 @@
+package com.pengrad.telegrambot.model.gift.unique
+
+data class UniqueGiftBackdrop(
+    @get:JvmName("name") val name: String,
+    @get:JvmName("colors") val colors: UniqueGiftBackdropColors,
+    @get:JvmName("rarityPerMille") val rarityPerMille: Int
+)

library/src/main/java/com/pengrad/telegrambot/model/gift/unique/UniqueGiftBackdropColors.kt

@@ -0,0 +1,8 @@
+package com.pengrad.telegrambot.model.gift.unique
+
+data class UniqueGiftBackdropColors(
+    @get:JvmName("centerColor") val centerColor: Int,
+    @get:JvmName("edgeColor") val edgeColor: Int,
+    @get:JvmName("symbolColor") val symbolColor: Int,
+    @get:JvmName("textColor") val textColor: Int
+)

library/src/main/java/com/pengrad/telegrambot/model/gift/unique/UniqueGiftModel.kt

@@ -0,0 +1,9 @@
+package com.pengrad.telegrambot.model.gift.unique
+
+import com.pengrad.telegrambot.model.Sticker
+
+data class UniqueGiftModel(
+    @get:JvmName("name") val name: String,
+    @get:JvmName("sticker") val sticker: Sticker,
+    @get:JvmName("rarityPerMille") val rarityPerMille: Int
+)

library/src/main/java/com/pengrad/telegrambot/model/gift/unique/UniqueGiftSymbol.kt

@@ -0,0 +1,9 @@
+package com.pengrad.telegrambot.model.gift.unique
+
+import com.pengrad.telegrambot.model.Sticker
+
+data class UniqueGiftSymbol(
+    @get:JvmName("name") val name: String,
+    @get:JvmName("sticker") val sticker: Sticker,
+    @get:JvmName("rarityPerMille") val rarityPerMille: Int
+)