Implemented the "copyItem(from: to: )" function for the FileService service in the library target.

Tests/Library/Helpers/Spies/FileServiceSpy.swift

@@ -18,6 +18,8 @@ extension FileServiceSpy: FileServicing {
         get async { .someCurrentFolder }
     }
     
+    func copyItem(from source: URL, to destination: URL) async throws (FileServiceError) {
+        actions.append(.itemCopied(source, destination))
     }
     
     func createFolder(at location: URL) async throws (FileServiceError) {
@@ -42,6 +44,7 @@ extension FileServiceSpy: FileServicing {
 extension FileServiceSpy {
     enum Action: Equatable {
         case folderCreated(_ location: URL)
+        case itemCopied(_ source: URL, _ destination: URL)
         case itemDeleted(_ location: URL)
         case itemExists(_ location: URL)
     }