[#54751] Meeting backlogs

[mrmir]

Ticket

https://community.openproject.org/work_packages/54751

What are you trying to accomplish?

One-time:

• [x] "Agenda backlog" for one-off meetings. This is a special section where agenda items can be added as a set of items that could possibly be added to that meeting
• [x] An empty meeting can still have a backlog, which is displayed below the empty blankslate
  • [x] This is possible when items have been added directly via work packages or when items in the meeting are manually removed and added to the backlog
• [x] The backlog section is displayed at the end of the meeting page and can be collapsed/expanded
• [x] Backlog state:
  • [x] Expanded by default when meeting is Open
  • [x] Collapsed by default when meeting is In progress
  • [x] Hidden when meeting is Closed
• [x] Backlog actions:
  • [x] Clear backlog (danger)
  • [x] + Agenda item
  • [x] + Work package
• [x] More actions for items:
  • [x] More action of every item in the backlog has a "Move to current meeting" action
  • [x] More action of every item NOT in the backlog has a "Move to backlog" action
  • [x] Backlog items have all regular more actions (edit, delete, etc.)
• [x] Users can drag items in from the backlog to add it to the agenda of a particular occurrence. They can also drag an agenda item into the backlog to remove it from the agenda of that meeting
• [x] Outcomes:
  • [x] Outcomes cannot be added to items in the backlog
  • [x] However, if an outcome already exists for an item that is then moved to the backlog, it retains it (same as open state of the meeting)
• [x] Adding an item to a one-time meeting adds it to the end of the agenda backlog

Series:

• [ ] The backlog is called "Series backlog"
• [ ] The backlog description is different
• [ ] The meeting updated flash works correctly
• [x] The backlog is hidden for the template
• [ ] Backlog actions are hidden for the template
• [ ] Drag and drop works from any occurrence
• [ ] Move to meeting/move to backlog work from any occurrence
• [ ] Blankslate acts as above
• [ ] Outcomes act as above
• [ ] Agenda items added to an occurrence get added to the series backlog
• [ ] The clear backlog dialog has different text

TODO

• [x] Add lookbook example for action button in the header in border_box_component_preview/collapsible
• [x] Clear backlog error handling
• [x] Make sure recurring meetings aren't showing backlogs/add feature flag
• [x] Update CollapsibleHeader to use slots that allow system arguments
• [x] Clicking doesn't work on page load sometimes
• [x] JS to remember state?
  • [ ] Code maintenance to add a data boolean collapsed/expanded to the primer component and use that in the stimulus controllers to detect state instead of the css class
  • [ ] Feature to make the collapsible header a drop zone when collapsed as well
• [x] Migration to create backlogs for all existing meetings
• [x] Backlog actions reset collapsed state
• [ ] New meeting create service spec
• [ ] Error when moving item to blankslate

Screenshots

What approach did you choose and why?

Merge checklist

• [ ] Added/updated tests
• [ ] Added/updated documentation in Lookbook (patterns, previews, etc)
• [ ] Tested major browsers (Chrome, Firefox, Edge, ...)