Description

This PR adds user tagging functionality to incident comments, allowing users to mention other team members in comments and send them notifications.

Features

• Users can mention others using the @ symbol in comments
• Mentions are visually highlighted in the comment thread
• Mentioned users receive real-time notifications
• Support for two mention formats:
  • Direct email mentions: @email@example.com
  • Display name with email: @Display Name email@example.com
• Keyboard navigation in the mentions dropdown

Technical Implementation

• Added CommentMention model and database migration
• Created MentionsInput component with autocomplete
• Added notification system for mentions
• Added end-to-end test for the feature

Testing

• Manual testing of the mention functionality
• Added E2E test for creating an incident with mentions /fixes #2187 /claim #2187