Add audio transcript and video description features for a11y

[AndreaBarbasso]

References

• Fixes [Accessibility] Media alternative for time-based content #3807
• Fixes [Accessibility] Providing labels for alternative content #3808
• Requires Add new metadata for bitstream submission form - audio and video a11y DSpace#12250

Description

Added new bitstream metadata in order to include an audio transcript and/or a video description to an audio/video bitstream. Managed such metadata in submission form and bitstream edit form. Introduced modals to show those values in the item page.

Instructions for Reviewers

List of changes in this PR:

• Changed the bitstream submission form to accommodate the newly created metadata fields;
• Applied a custom logic to show/hide fields relevant to the selected media type;
• Extended the current bitstream edit form to - again - accommodate these new metadata fields;
• Introduced clickable links to show audio transcripts and video descriptions in a modal above the item page.

Include guidance for how to test or review your PR.

• Create a new Item and upload a bitstream. Try to change its media type - an audio media should show the audio transcript textarea, a video media should show the video description textarea, and an audio and video media should show both;
• Confirm that these values are saved correctly as bitstream metadata;
• Confirm that changing the media type does not delete metadata that is not relevant anymore (e.g. selecting the video media type should not clear the audio transcript metadata value. This is expected - since these values can be quite long and tedious to write, changing the media type by accident should not clear them;
• After depositing the item, check that its bitstream metadata can be changed. The bitstream edit form should behave the same as the submission form;
• Check that the item page shows links relevant to the bitstream type. An audio bitstream with an audio transcript should show the transcript link, etc;
• Check that clicking on those links open a modal with the metadata value shown inside.

Checklist

• My PR is created against the main branch of code (unless it is a backport or is fixing an issue specific to an older branch).
• My PR is small in size (e.g. less than 1,000 lines of code, not including comments & specs/tests), or I have provided reasons as to why that's not possible.
• My PR passes ESLint validation using npm run lint
• My PR doesn't introduce circular dependencies (verified via npm run check-circ-deps)
• My PR includes TypeDoc comments for all new (or modified) public methods and classes. It also includes TypeDoc for large or complex private methods.
• My PR passes all specs/tests and includes new/updated specs or tests based on the Code Testing Guide.
• My PR aligns with Accessibility guidelines if it makes changes to the user interface.
• My PR uses i18n (internationalization) keys instead of hardcoded English text, to allow for translations.
• My PR includes details on how to test it. I've provided clear instructions to reviewers on how to successfully test this fix or feature.
• If my PR includes new libraries/dependencies (in package.json), I've made sure their licenses align with the DSpace BSD License based on the Licensing of Contributions documentation.
• If my PR includes new features or configurations, I've provided basic technical documentation in the PR itself.
• If my PR fixes an issue ticket, I've linked them together.

[tdonohue]

@AndreaBarbasso : I'm starting to review this work, and I'm a little confused about the implementation that you've created, as it doesn't appear to align with the tickets #3807 and #3808:

• In #3807, we've noted that WCAG requires either an audio/video description/transcript or a full text alternative.
• In #3808 we also talk about allowing an upload of full text alternative content and labeling it appropriately

This PR appears to only add a way to create a description/transcript. It doesn't fix the issues with uploading alternative content & relating it back to the original file.

I was expecting to have two a11y features implemented:

1. An option to add a description/transcript for the Bitstream (ideally in a dc.description metadata field, as that already exists).
2. An option to upload a secondary file which provides a textual alternative to audio/video content.

This PR currently only implements the description/transcript feature. It doesn't allow for alternative content. So, it appears to be a partial fix for #3807 and doesn't solve #3808 at all.

My opinion is that we can simplify this PR's functionality to just have a single Description metadata field which can capture either a transcript (for audio) or a description (for video). I'm not sure that we need two separate metadata fields (description and transcript), especially if we are going to implement the alternative content upload option.

I added more feedback to the backend PR as I feel we should use existing metadata fields as much as possible.