MacOS app does not utilise sandboxing.

[duck09]

• This is not a feature request (existing functionality does not work, not missing functionality).
  I will request features on forum or via support.
• I've searched and did not find a similar issue.

Describe the bug
The Tuta Mail MacOS app does not utilise MacOS' native sandboxing which greatly improves security. This should be done especially since this is a sensitive app.

To Reproduce
Steps to reproduce the behavior:

1. Launch Tuta Mail on MacOS
2. Open Activity Monitor
3. Enable the "Sandbox" column under View -> Columns -> Sandbox
4. View the column "Sandbox"
5. See that Tuta Mail is not sandboxed.

Expected behavior
Tuta Mail desktop app is sandboxed on MacOS.

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: [MacOS]
• Version [All versions]

Additional context
(https://developer.apple.com/documentation/xcode/configuring-the-macos-app-sandbox)