Refine error handling in RequestHandler and the console slightly (#2177)

If we don't explicitly handle random unexpected exceptions, the error
that the front end receives includes a big ole stacktrace, which is
unhelpful for regular users and possibly bad to expose. Instead, we
should provide a vague "something went wrong" message.

Separately, we can create a default SnackBar options and use that (we
want it longer than 1.5 seconds because that's pretty short).

console-webapp/src/app/settings/security/security.component.ts

@@ -64,9 +64,7 @@ export default class SecurityComponent {
         this.resetDataSource();
       },
       error: (err: HttpErrorResponse) => {
-        this._snackBar.open(err.error, undefined, {
-          duration: 1500,
-        });
+        this._snackBar.open(err.error);
       },
     });
     this.cancel();