API reference uplift

[jstirnaman]

Improve API reference docs for UX and performance.
Replace ReDoc

To do:

• Generate Hugo pages for endpoints and OpenAPI operations in the spec.
• Use Rapidoc to render generated spec pages
• Implement theme switching.
• Set API server to the user's configured docs site URL.
• Show page title
• Use tag name as nav link
• Use tag name as page title
• Expand/collapse API servers section
• Use only one tag per path--provides a title-name and description for the path
• Add Using the <name> API page with traitTag content
• Remove traitTags from paths
• Move related links from description body to related frontmatter
  • Replace or ReDoc endpoint tag references with new URLs
  • Replace or alias outdated and broken site links.
• Fix nested scrollbar
• Fix styles
• Fix index page descriptions (use Rapidoc mini or docs-native endpoint shortcode)

[jstirnaman]

Closed with #6622