Notify by email when manual job fails but job is allowed to fail

Description

As requested by customer:

I'm using a manual job to deploy to production, and I understand from reading the docs here that manual jobs are "allowed to fail" by default. I understand the reasons for this. Indeed, I don't want the pipeline to be blocked by the manual job, particularly since not every pipeline will be deployed to production in my specific workflow. However, I would still like to receive an email when a manual job fails.

Have tested on GitLab.com and confirmed that failed manual jobs do not send a notification.

Proposal

Notify by email when manual job fails but job is allowed to fail. Perhaps this could be an option box in pipeline settings?

Links / references

https://gitlab.zendesk.com/agent/tickets/84026 (internal)

Documentation blurb

Notify by email when job fails, even if job is allowed to fail.

Overview

What is it? Why should someone use this feature? What is the underlying (business) problem? How do you use this feature?

Use cases

Who is this for? Provide one or more use cases.

Feature checklist

Make sure these are completed before closing the issue, with a link to the relevant commit.