feat: support @mentioning user groups in ticket comments

[ManyaGirdhar]

Description

Adds support for @mentioning User Groups in ticket comments. Previously,
only individual agents could be mentioned. Tagging a User Group now sends
an HD Notification to all members of that group.

Relevant Technical Choices

• extract_mentions in utils.py now returns a type field (user or group) by checking if data-id contains @. User emails always contain @, User Group names never do.
• notify_mentions in mixins/mentions.py expanded to resolve group mentions into individual member notifications via User Group Member doctype.
• frappe.db.exists("User Group", mention.email) guard ensures Agent document names without @ are not mistakenly treated as groups.

Testing Instructions

1. Open any ticket in Helpdesk
2. Type @ in the comment box
3. Select a User Group and submit the comment
4. Verify HD Notification is created for each member of the group
5. Verify tagging an individual agent still works correctly

Screen.Recording.2026-03-14.at.11.15.52.PM.mov

[codecov]

Codecov Report

❌ Patch coverage is 86.36364% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 51.30%. Comparing base (0d4ca83) to head (4199b3a).
⚠️ Report is 8 commits behind head on develop.

Files with missing lines	Patch %	Lines
helpdesk/mixins/mentions.py	85.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3124      +/-   ##
===========================================
+ Coverage    51.23%   51.30%   +0.07%     
===========================================
  Files          122      122              
  Lines         5420     5432      +12     
===========================================
+ Hits          2777     2787      +10     
- Misses        2643     2645       +2     

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[RitvikSardana]

@ManyaGirdhar

Hey

we should not do user groups
as some of the users in the user group might not be agents, and the context in the reply area is to tag Agent(s)

Best is, to use HD Team doctype and tag a team

[ManyaGirdhar]

@ManyaGirdhar

Hey

we should not do user groups as some of the users in the user group might not be agents, and the context in the reply area is to tag Agent(s)

Best is, to use HD Team doctype and tag a team

@RitvikSardana
Updated the PR to use HD Team doctype instead of User Group. The mention dropdown now shows HD Teams alongside agents, and notifications are sent to HD Team members via the HD Team Member child table.

Screen.Recording.2026-04-13.at.12.07.14.PM.mov