Port MASTG-TEST-0073 (by @guardsquare)

[pascalj]

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This PR closes #2966

[pascalj]

A couple of comments:

• Persistence is handled automatically with iOS 10.0, i.e. if you have sensitive data just don't add it to the generalPasteboard. All app-specific pasteboards are not persistent.
• Handoff is handled securely and locally (BLE and Wifi like Airdrop), so I think it doesn't pose an additional risk.
• Since iOS 14 the user must show intent to allow apps to read from the pasteboard which makes this only a risk when you consider user error as a threat.