Updating IRIS Alerter to use ElastAlert Alerter defaults

[bvirgilioamnh]

Description

Currently the IRIS alert uses rule supplied values for the description and simply uses the rule title for the alert title. This significantly reduces the ability to dynamically create/repurpose alerts as the rule creator must tailor each individual alert with a custom description. Additionally this description field as it stands does not resolve any variable or template fields resulting in a static description for all alerts.

This PR aims to resolve this by using the built in create_alert_body() and create_title() functions within the Alerter class.

As this is possibly a breaking change I'm opening this PR as a draft for discussion.

Checklist

• [x] I have reviewed the contributing guidelines.
• [ ] I have included unit tests for my changes or additions.
• [ ] I have successfully run make test-docker with my changes.
• [ ] I have manually tested all relevant modes of the change in this PR.
• [ ] I have updated the documentation.
• [ ] I have updated the changelog.

Questions or Comments

Do not merge this PR until discussed! :)