Add existing unit workflow (course level)

[sdaitzman]

Modify empty case of new unit at both course overview level and unit page level: add your own component or reference an existing unit page → overlay sidebar, pick library, pick unit

[jmakowski1123]

Minimal implementation:

• Only reuse workflow option is via the course outline page
• From the content outline page, under the "units", add a new button under "add unit" and "paste unit" for "use unit from library"
• Library search modal opens from the course outline page
• Units can be added one at a time (same as the component reuse workflow)

[ChrisChV]

Hi @jmakowski1123 @sdaitzman @edschema, This is almost implemented in #1829. I'm attaching a video showing how the workflow is looking, so you can review. Thank you!

https://www.loom.com/share/1133a3dfbbd349b18c7cf4aca2023e78?sid=aa774d65-5321-4476-95b5-0987f4a49ccf

[jmakowski1123]

This is looking great Chris, thank you. This will absolutely work for the MVP.

At some point, we'll probably want to add the toast notification, but I think it's ok to go without it temporarily. Not a blocker.

[ChrisChV]

@jmakowski1123 @sdaitzman @edschema This is ready for AC testing on the sandbox

[edschema]

Thank you Chris! I have three notes, though I do not believe the third is an actual issue but a bug in the testing environment.

1. In successfully added units, the "add new component" widget appears sometimes. I'm not sure exactly what conditions cause it to appear and not appear, however I noticed it appears after publishing a unit, but not after a subsequent refresh of the page.

2. In the "add existing unit" modal, the preview shows draft versions of units. ie: if a unit is published with 2 components, then a third component is added within the library, but the component and unit are not published, the preview for the unit shows three components. If you open the sidebar, it also shows three components.

3. I do not think this is an issue because it appears this behavior only happens with units created before this story was built, but never-published units (that were created prior to "add existing unit" feature) are showing up for me in the 'add unit' modal. I'm able to select and click 'add to unit.' Upon refresh, an empty unit appears
   https://github.com/user-attachments/assets/be87abe5-3ef3-4643-9700-c7cd0e7fc224
   Units created AFTER are not appearing in the "add to unit" modal, so I do not think this is an actual issue?

[pomegranited]

@ChrisChV FYI

In the "add existing unit" modal, the preview shows draft versions of units.

As part of #1778, I will be updating the search index to provide both published and latest draft versions of the Unit data in the search index, so you can source published data in this view.