Label issues opened by Prometheus alerts with `incident`

Problem to solve

GitLab users use issues for many things. As we start to build out Incident Management within GitLab, we need a way to differentiate between issues being used as incidents and other issues. This solves the following problems:

1. To build out feature around incidents (Post incident reviews, Incident triage dashboard, etc) we need a way to indicate an issue is an incident
2. DevOps teams need an easy way to search for incidents, create boards
3. First iteration of Incident Triage Dashboard could be an issue board based on the Incident label

Intended users

Sasha the Software Developer
Devon the DevOps Engineer
Sidney the Systems Administrator

Further details

This work contributes to the Incident Management Vision

Proposals

1. When the Alert bot creates an issue for the first time in a GitLab instance, check to see if incident is an existing label and if it does not exist, create it.
2. Automatically add the incident label to all issues created by the Alert bot
3. Incident label can be manually removed from incidents by users

Permissions and Security

Anyone who can interact with issues and add labels to them

Documentation

Testing

What does success look like, and how can we measure that?

Links / references