Show error if we fail to reset defences

[gsproston-scottlogic]

Bug report

Description

Pressing the 'reset' button will always show the confirmation message, even if the reset HTTP request fails. We should show an error instead.

Reproduction steps

Steps to reproduce the behaviour:

1. Don't run the backend
2. So to sandbox mode
3. Expand a configurable defence, e.g. character limit
4. Press the reset button
5. Confirmation shown

Expected behaviour

Show an error if the reset fails.

Screenshots

Software (please complete the following information):

• Browser: Edge

Acceptance criteria

GIVEN the backend is down
WHEN the reset button is pressed
THEN an error message is shown