Add count tracking to NanoTDFManager

A count property has been introduced to the NanoTDFManager to keep track of the number of NanoTDFs. Functions have been adjusted to increment/decrement the count when NanoTDFs are added/removed. Additionally, a new getCount function has been introduced to retrieve the count.

OpenTDFKit/NanoTDFManager.swift

@@ -2,9 +2,11 @@ import Foundation
 
 class NanoTDFManager {
     private var nanoTDFs: [Data: NanoTDF] = [:]
+    private var count: Int = 0
 
     func addNanoTDF(_ nanoTDF: NanoTDF, withIdentifier identifier: Data) {
         nanoTDFs[identifier] = nanoTDF
+        count += 1
     }
 
     func getNanoTDF(withIdentifier identifier: Data) -> NanoTDF? {
@@ -16,6 +18,16 @@ class NanoTDFManager {
     }
 
     func removeNanoTDF(withIdentifier identifier: Data) {
-        nanoTDFs.removeValue(forKey: identifier)
+        if nanoTDFs.removeValue(forKey: identifier) != nil {
+            count -= 1
+        }
+    }
+
+    func isEmpty() -> Bool {
+        return nanoTDFs.isEmpty
+    }
+
+    func getCount() -> Int {
+        return count
     }
 }