web_timeline: display an item multiple times when grouping by many2many

[huguesdk]

currently, when grouping by a many2many field, if it contains multiple values (for example: a task assigned to more than one person), the item will only be displayed in the first group.

this is a known limitation listed in the readme.

the goal of this issue is to discuss about how to fix this. could the author or maintainer give some information about the reasons that it is not yet done, what would be needed to do it and the possible issues?

i think we should consider this a bug, as the list and kanban views correctly display the item multiple times (because they make one web_search_read request per group).