Add e-mail recipients in case of failure in job/build definition

[skakim]

Is your feature request related to a problem? Please describe.
It would be nice to be able to set a set of e-mail addresses to automatically send an e-mail in case of failure of a job or build. This could be used to increase transparency to non-PR related builds (for example, cronjob builds).

Describe the solution you'd like
Something like for jobs:

{
        "type": "docker",
        "name": "build",
        "docker_file": "infrabox/build-and-test/Dockerfile",
        "command": ["echo", "hello world"],
        "resources": { "limits": { "cpu": 1, "memory": 1024 } },
        "build_only": false,
        "build_context": "...",
        "cache": { ... },
        "timeout": 3600,
        "depends_on": ["other_job_name"],
        "environment": { ... },
        "build_arguments": { ... },
        "deployments": [ ... ],
        "security_context": { ... },
        "repository": { ... },
        "registries": [ ... ],
        "e-mails": [ "john.doe@gmail.com" ]
    }

and for builds:

{
    "version": 1,
    "jobs": [
        ...
    ],
    "e-mails": [
       "john.doe@gmail.com"
    ]
}

In the background, Infrabox will send an e-mail to the recipients warning them if the job/build failed.

The e-mail itself, could have a Report similar to the "Tests" tab, showing the failed jobs (in case of failed build) and failed tests (for all jobs that failed, in case of failed build), with links to facilitate their job. This is an advanced suggestion (a big nice-to-have), being able to automatically sending failure e-mails is the core part of this Feature request.

Describe alternatives you've considered
Right now the e-mail sending needs to be implemented in the job itself, and for build failure it needs to be implemented as a job that runs in the end. This is not ideal.

Additional context
Add any other context or screenshots about the feature request here.