support for disabled elements for screen readers

[jensvannerum]

References

Add references/links to any related issues or PRs. These may include:

• Fixes The log in button is not fully accessible to users using a screen reader #3249
• 8.x version in [Port dspace-8_x] support for disabled elements for screen readers #3269
• 7.x version in [Port dspace-7_x] support for disabled elements for screen readers #3270

Description

Replaced the html disabled attribute with a custom directive which has the same effect.
The directive is however friendly for screen readers using aria attributes and being focusable with keyboard navigation

Instructions for Reviewers

• Go to any page that uses a disabled state (e.g login page) and verify behaviour is as expected.
• Verify the aria-disabled attribute is present on the disabled element for the screen reader

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[github-actions]

Hi @jensvannerum,
Conflicts have been detected against the base branch.
Please resolve these conflicts as soon as you can. Thanks!

[tdonohue]

@jensvannerum : We gave this a group review in our Developer Meeting today. Overall the feedback was positive, but I've added a few notes inline on issues found during the meeting (and just after the meeting as I scanned it again).

Also noted in the meeting is that we should add a note to our Accessibility documentation guidelines about this new dsDisabled directive (and to avoid using disabled). We have a page with very basic notes in both the 7.x and 8.x docs:

• 7.x docs: https://wiki.lyrasis.org/pages/viewpage.action?pageId=313851976#UserInterfaceDesignPrinciples&Accessibility-UserInterfaceAccessibilityGuidelines
• 8.x docs: https://wiki.lyrasis.org/pages/viewpage.action?pageId=315720834#UserInterfaceDesignPrinciples&Accessibility-UserInterfaceAccessibilityGuidelines

[jensvannerum]

@tdonohue Thanks for the feedback, I feel like I addressed all of it.

Note that I also reduced the scope of this PR a little, the directive is currently only present on buttons.
I did this because developers might otherwise expect this to replace the disabled attribute of HTML everywhere, which isn't the case yet. It would disable keystrokes and mouse clicks but wouldn't have the same "disabled look" as the actual HTML attribute gives it (90% usage of the disabled attribute in DSpace is on button anyways so still a huge improvement for accessibility).

Backported changes to 8.x and 7.x PR's too