Add "Limits to Tags" for Alerts

[sithmein]

Current Behavior

Alerts can be limited to projects. Policies can be limited to projects and tags.

Proposed Behavior

It should be possible to limit alerts also to tags. We have many teams working with DT and we tag all projects with team names. We want to send alerts to teams only for "their" projects.

Checklist

• [X] I have read and understand the contributing guidelines
• [X] I have checked the existing issues for whether this enhancement was already requested

[sebD]

Hi, I have started working on it.