[Issue Alerts] Allow user details to be used as tags in Slack notifications

[FeBe95]

Problem Statement

When creating/editing an issue alert rule, you can provide a comma-separated list of addition tags to append to a Slack notification.

I see two problems with this feature:

1. There are no clues indicating which tags can be entered. The input is a simple text field and does not offer any kind of autocomplete.
2. There are tags that don't seem to be valid here, for example user details.
   • E.g., I wanted to append the email of the affected user to the Slack notification.
   • I tried user.email, user_email, email, User: Email, "User: Email".
   • None of them worked.

URL

https://<organization>.sentry.io/issues/alerts/rules/<project>/<rule-id>/

Screenshot

Solution Brainstorm

1. Provide a list of available tags when the input is selected, for example via auto-completion, a drop-down or a multi-select list in a modal.
2. Add user details to the list of available tags.

Product Area

Alerts

[linear]

ENG-5974

[getsantry]

Auto-routing to @getsentry/product-owners-alerts for triage ⏲️

[cathteng]

Hi, we are working on a revamp of the UI and are looking into how to make the tags experience better. Thanks for the feedback!