US-40 — Error handling

## User story

_As an App Alert notification author, I want to know, and for others to know, that a send has fully or partly failed so that I can make a decision as to what to do next_

## Acceptance scenarios

```gherkin

Feature: Handle a failed notification send

Background:
Given a notification has been submitted for delivery
And the notification has at least one communication channel selected
And the author of the notification is known

Scenario: Send fails and the author is told what went wrong
When delivery to a communication channel fails or partly fails
Then the notification status in history should become "failed"
And the failure reason should be recorded against the notificatio
And the failure message should name the notification by its title
And the failure message should state which communication channel failed
And the failure message should state whether any recipients received the notification
And the failure message should describe the cause in plain language
And the failure message should offer a single primary action to resolve the failure

Scenario: Failure is shown in the history list
When delivery fails
Then the notification should appear in the list with status "failed"
And selecting the notification should show the full failure detail