Window grabs focus for connection errors

[opk12]

Description

Because of the certificate error message boxes from #815, Quaternion's window is randomly brought to the top and grabs the keyboard/mouse focus, interrupting my work. Until there is a mechanism to save the self-signed certificate locally, the errors could at least be less intrusive and only show up when I switch to Quaternion's window.

Version information

Quaternion 0.0.95.1 on Fedora 35 Quaternion 0.0.9.5 on Debian 11

[opk12]

For example, LibreOffice's notification bar at the top for the read-only mode (screenshot) has the summary, a button to take action, and a cross to close it.