Add alt text field to widgets

[alundgard]

This summary issue covers some of the alt text requirements listed in #2462. Specifically: adding alt text via the widgets, excluding adding alt text via the Curation > Items dashboard.

The scope for initial implementation (Stanford Work Cycle Fall 2024) will be limited to widgets that display images as static images (i.e., widgets that do not embed images via zoomable viewers like Mirador and OpenSeadragon).

In scope: Item Grid, Item Row, Uploaded Item Row, Item Slideshow, Item Carousel
Out of scope: Item Embed

• Add alt text field to Item Grid widget #2569

• Add alt text field to Item Row widget #2570

• Add alt text field to Uploaded Item Row widget #2571

• Add alt text field to Item Carousel widget #2572

• Add alt text field to Item Slideshow widget #2573

• The current default functionality for most of the In scope widgets (Item Grid, Item Row, Item Carousel, Item Slideshow) is to use the item's metadata title as the alt text.

• The Uploaded Item Row widget appears to default to null alt text, which may incorrectly indicate that the uploaded image is decorative. However, if the Link URL and Caption fields are populated, the widget uses the Caption field as the alt text.

• Adding an alt text field to these widgets will allow curators to improve or correct their default functionality—to add custom alt text or set images as decorative, as appropriate.

Notes

• The team considered introducing functionality for adding alt text to each item via the Curation > Items dashboard. It was determined that this functionality did not satisfy a strong user need, and would complicate the higher-priority implementation of adding alt text via the widgets.