Is your feature request related to a problem? Please describe.
Currently, users can communicate in the group chat, but there's no way to mention/tag specific users using @username. This makes it difficult to direct messages at particular participants, especially in larger group conversations

Describe the solution you'd like
I'd like to introduce user tagging via @ in the chat input, similar to how platforms like Slack or WhatsApp handle mentions. Here's what I envision:
When the user types @, a searchable list of group members should appear.
Selecting a user auto-completes the @username in the chat input.
When the message is sent, the mention is visually distinct (e.g. bold, colored).
The backend may optionally store tagged users (e.g. via user ID for notifications or metadata).
(Optional) Tagging a user could notify them directly via push/email.

Describe alternatives you've considered
Manual mentions: Users just type someone's name manually, but this lacks structure, styling, and can't be tied to actual users for notifications.

Highlight keywords: Some chats use #hashtags or keywords, but this doesn't help with user-specific tagging.

Additional context
The project is using the chatview package for the Flutter frontend.
Tagging should work with TextFieldConfiguration inside SendMessageConfiguration.
Ideal for teams, communities, or customer support scenarios.
Screenshots from Slack, Discord, or WhatsApp mentions can serve as UI inspiration.