delete old labels when a new label list is fetched

apple/OmnivoreKit/Sources/Services/InternalModels/InternalLinkedItemLabel.swift

@@ -110,9 +110,22 @@ extension Sequence where Element == InternalLinkedItemLabel {
     var result: [NSManagedObjectID]?
 
     context.performAndWait {
+      // Get currently stored label ids so we can later delete the old ones
+      let labelsFetchRequest: NSFetchRequest<Models.LinkedItemLabel> = LinkedItemLabel.fetchRequest()
+      let existingLabels = (try? labelsFetchRequest.execute()) ?? []
+
+      let validLabelIDs = map(\.id)
+      let invalidLinkedItemLabels = existingLabels.filter { !validLabelIDs.contains($0.unwrappedID) }
+
       let labels = map { $0.asManagedObject(inContext: context) }
+
       do {
         try context.save()
+        // Delete all existing labels that aren't part of the newly updated list
+        // received from the server
+        for linkedItem in invalidLinkedItemLabels {
+          context.delete(linkedItem)
+        }
         logger.debug("labels saved succesfully")
         result = labels.map(\.objectID)
       } catch {