Swift 4 vCard on touch add to contacts

Question

I have scoured the internet looking to find a way to save a persons contact information. Currently on my mobile website I have a vCard that when clicked on a phone asks the user if they would like to add the contact to their contacts. In swift however loading that same link generates a 404 error page. So how would I go about doing this? I want when the user clicks on the icon a pop up displays asking the user if they want to save the contact to their phone. The data is being pulled in through a json api. I assume I need to take this data and format it in a specific way. Any suggestions or pointers in a direction to take this is much appreciated.

Thanks

Update: Here is my attempt at some code for this. When this prints to the console I get the vcard output, but an error is thrown on the JSONSerialization. Maybe someone can point me in the right direction.

@IBAction func contactTapped(_ sender: Any) {
    let contact = createContact()
    do {
        try shareContacts(contacts: [contact])
    } catch {
        print("Error printing contact")
    }
}

func shareContacts(contacts: [CNContact]) throws {
    guard let directoryURL = FileManager.default.urls(for: .cachesDirectory, in: .userDomainMask).first else {
        return
    }
    var filename = NSUUID().uuidString

    if let contact = contacts.first, contacts.count == 1 {
        if let fullname = CNContactFormatter().string(from: contact) {
            filename = fullname.components(separatedBy: " ").joined(separator: "")
        }
    }
    let fileURL = directoryURL
    .appendingPathComponent(filename)
    .appendingPathComponent("vcf")

    let data = try CNContactVCardSerialization.data(with: contacts)

    print("filename: \(filename)")
    print("contact: \(String(describing: String(data: data, encoding: String.Encoding.utf8)))")

    try JSONSerialization.data(withJSONObject: JSONEncoder(), options: JSONSerialization.WritingOptions.prettyPrinted)

    let activityViewController = UIActivityViewController(
        activityItems: [fileURL],
        applicationActivities: nil
    )

    present(activityViewController, animated: true, completion: {})
}

func createContact() -> CNContact {

    // Creating a mutable object to add to the contact
    let contact = CNMutableContact()

    contact.imageData = NSData() as Data // The profile picture as a NSData object

    contact.givenName = fullNameLbl.text!
    //contact.familyName = "Appleseed"

    let workEmail = CNLabeledValue(label:CNLabelWork, value: emailLbl.text! as NSString)
    contact.emailAddresses = [workEmail]

    contact.phoneNumbers = [CNLabeledValue(
        label:CNLabelPhoneNumberiPhone,
        value:CNPhoneNumber(stringValue: phoneLabel.text!))]

    let store = CNContactStore()
    let saveRequest = CNSaveRequest()
    saveRequest.add(contact, toContainerWithIdentifier: nil)
    try! store.execute(saveRequest)

    return contact
}