Correct accessibility issues with dynamic content updates

[glowcloud]

Swagger UI has multiple buttons that dynamically change the content of the page. Users navigating the website with a screen reader might not know that anything changes, as there is no indication that it does, e.g.:

• no indication that there are validation errors when authorizing or that the authorization was successful (note: there is also no visual indication that the fields have validation errors)

• no indication that inputs become enabled when clicking on Try it out button

• no indication that there are validation errors or that the request was successful after clicking on Execute button in Try it out

• the fields with validation errors are not focused after clicking on Execute button

• no indication what was copied or that it was successful when clicking on Copy to clipboard button

We could possibly address it with: https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Guides/Live_regions

This task covers issues originally reported in:

• [Accessibility] WCAG 2.1 1.3.1, and 4.1.2 && Section 508 502.3.1 && Screen Reader Usability #5248
• Swagger UI is not accessible compliant #7350