user_groups: Add support to set can_mention_group during creation.

This commit adds API support to set can_mention_group while
creating a user group.

Fixes a part of #25927.

zerver/actions/user_groups.py

@@ -1,5 +1,5 @@
 import datetime
-from typing import Dict, List, Optional, Sequence, TypedDict
+from typing import Dict, List, Mapping, Optional, Sequence, TypedDict
 
 import django.db.utils
 from django.db import transaction
@@ -37,14 +37,20 @@ def create_user_group_in_database(
     *,
     acting_user: Optional[UserProfile],
     description: str = "",
+    group_settings_map: Mapping[str, UserGroup] = {},
     is_system_group: bool = False,
 ) -> UserGroup:
     user_group = UserGroup(
         name=name, realm=realm, description=description, is_system_group=is_system_group
     )
-    system_groups_name_dict = get_role_based_system_groups_dict(realm)
-    user_group = set_defaults_for_group_settings(user_group, system_groups_name_dict)
 
+    for setting_name, setting_value in group_settings_map.items():
+        setattr(user_group, setting_name, setting_value)
+
+    system_groups_name_dict = get_role_based_system_groups_dict(realm)
+    user_group = set_defaults_for_group_settings(
+        user_group, group_settings_map, system_groups_name_dict
+    )
     user_group.save()
 
     UserGroupMembership.objects.bulk_create(
@@ -150,12 +156,18 @@ def check_add_user_group(
     name: str,
     initial_members: List[UserProfile],
     description: str = "",
+    group_settings_map: Mapping[str, UserGroup] = {},
     *,
     acting_user: Optional[UserProfile],
 ) -> UserGroup:
     try:
         user_group = create_user_group_in_database(
-            name, initial_members, realm, description=description, acting_user=acting_user
+            name,
+            initial_members,
+            realm,
+            description=description,
+            group_settings_map=group_settings_map,
+            acting_user=acting_user,
         )
         do_send_create_user_group_event(user_group, initial_members)
         return user_group