Add error messages (e.g. creating terms) within user interface

At the moment one gets redirected to a new page that displays the error message. It would be more user friendly to display the error directly in the user interface so the user doesn't has to click on the back button, open the "Create terms" dialogue again etc.
Same applies to other errors like "Cannot kick last owner".

Locate the Create terms dialogue and trace the current error-page or redirect flow. Then inspect the analogous “Cannot kick last owner” error path in the user interface. The work is done when these errors are shown in their relevant interface context without requiring back navigation.

Written by the indexing model from the issue text.