Group items in shopping lists based on labels (#319)

* Add data classes to hold food label information

- Created `GetFoodLabelResponse` data class to represent food label details
- Updated `GetFoodResponse` to include `label` property of type `GetFoodLabelResponse`

* Add backend to sort items in shopping lists by label

* Add UI code to sort items in shopping lists by label

* Use label from ShoppingListItem instead of Food

* Use list for ShoppingListItems and labels storage

* Fix incorrect routing code

* Only add DefaultLabel if there are items with a label

* Small improvements to comments and formatting

datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/models/GetItemLabelResponse.kt

@@ -0,0 +1,12 @@
+package gq.kirmanak.mealient.datasource.models
+
+import kotlinx.serialization.SerialName
+import kotlinx.serialization.Serializable
+
+@Serializable
+data class GetItemLabelResponse(
+    @SerialName("name") val name: String,
+    @SerialName("color") val color: String,
+    @SerialName("groupId") val grpId: String,
+    @SerialName("id") val id: String
+)

datasource/src/main/kotlin/gq/kirmanak/mealient/datasource/models/GetShoppingListResponse.kt

@@ -23,6 +23,7 @@ data class GetShoppingListItemResponse(
     @SerialName("quantity") val quantity: Double = 0.0,
     @SerialName("unit") val unit: GetUnitResponse? = null,
     @SerialName("food") val food: GetFoodResponse? = null,
+    @SerialName("label") val label: GetItemLabelResponse? = null,
     @SerialName("recipeReferences") val recipeReferences: List<GetShoppingListItemRecipeReferenceResponse> = emptyList(),
 )