Warn macOS user that he has disabled microphone access

**Has this feature been discussed and generally agreed?**

No, but it should be an easy task to do.

**Describe the solution you'd like**

If a macOS user has disabled microphone access by wrongly selecting don’t allow microphone access, it might get confusing why the microphone "doesn’t work".

There should be a warning message which is invoked once you connect to a server which hints you at the problem.

This message should

1. Not stop the user from connecting to a server (maybe he’s just a listening client?)
2. Have a button to open privacy settings

Can’t work on it right now, so I‘d be happy if a macOS dev would look at it.

No files or tests are named. Start by tracing the macOS connection flow and microphone-permission handling; the change is done when a denied microphone permission produces a non-blocking warning with a button to open privacy settings, while still allowing connection.

Written by the indexing model from the issue text.