Add support for linked SingleItem in holdings

[olovy]

Checklist:

• I have run the unit tests. yarn test:unit
• I have run the linter. yarn lint

Description

Add support for SingleItems (sv: exemplar) in holdings.
Initially to be used for pinpointing itemUsed in digital reproductions.

An Item in hasComponent can be converted to a SingleItem.
It looks similiar to when extracting linked works.

The single items are always stored in their own records and linked from the the holding record.
Note the id in the top right corner.

But they can be edited in place as if the were part of the same record.

There are separate options for removing the linked entity or just the link.
Reused the ❌ for removing links. Maybe needs to be more obvious.

There can of course be many linked items and mixed with local items.

The feature is currently only available for sigel S.

Depends on libris/definitions#494
Depends on libris/librisxl#1467

Tickets involved

LXL-4504

Summary of changes

• Add settings.extractableMappedTypes that specifies which types can be extracted and which type they should be converted to. That is, Item can be extracted to its own document and should then be converted to 'SingleItem. This is a bit clumsy but does the job for now.

• When loading a record/document, other documents that should be inlined are moved from quoted to the main inspector data.

  • This is done for linked things in properties with category compositional (only hasComponent...).
    • TODO? Should be compositional + integral
  • Their ETags are fetched and stored for later use.
  • We count on embellish data to include the whole docs and don't fetch the doc data separately.

• When saving, inlined documents are extracted and updated before the main document in separate requests.

• Inlined records that should be deleted are deleted after the main doc is saved (this might fail...).

• 81208b0 breaks out the id-pill used in the top right corner of entity-summary to its own component. Taken from Feature/lxl 4504 cataloguing items #1073

• bcf023b contains the main changes.

• The other commits just remove obsolete and dead code that I encountered.

Not in scope

There is no way to move (link) a SingleItem to another holding record.

TODO

• Check MARC21 conversion
• Don't include inlined documents in "Download as JSON-LD" (?)
• Duplicating or copying a SingleItem creates a local SingleItem. Is this desired?
• Handle deletion of the whole holding?
• Future: have a way to update multiple records atomically.

[olovy]

!isExtracting is a workaround for a bug in the old "extract" code.
If you start extracting an entity and then delete it you get an error when saving.

It is still possible to trigger:

• Add a new Item in hasComponent
• Click "Extract Single item" / "Extrahera Exemplar"
• Click Undo (removing the added item)
• Save
• Error!

[jesperengstrom]

LGTM!

Must say I have little knowledge of this part of the code, but all looks reasonable. Nice cleaning job too.

Have tried creating/extracting, editing, viewing (both inline and on its own) and unlinking/deleting singleItems. Seems to work as expected.

The only thing I noticed is an alert saying I have unsaved changes when I try to navigate away in edit mode, even if I save and try again. Using the green button does it. Maybe it’s always been like this.