Feature: Save FTP credentials

### Description

Hello,

when adding an ftp connection, it asks for the username and password, I enter them and access the NAS server. It works. I can see the directory structure of the server.
But if I close "Files" and open it again, it asks for the username and password again.

Symptom: does not save username and password.

Can you help me with this?

Thanks:
Peter

### Steps To Reproduce

1. Open FILES
2. Add NAS server with FTP
3. enter user and password
4. everything is OK
5. Close FILES
6. Open FILES
7. To access the NAS server, the user name and password must be entered again

### Steps to fix

But if I close "Files" and open it again, it asks for the username and password again.

### Files Version

Verzió: 2.3.12.0 OS

### Windows Version

Version: 10.0.19043.1466

### Relevant Assets/Logs

[Uploading debug.log…]()
[debug_fulltrust.log](https://github.com/files-community/Files/files/10004756/debug_fulltrust.log)