Dashboard Extensibility

[grolu]

Allow to extend the dashboard with custom add-ons, like new cloud infrastructure types without modifying the Dashboard core. This allows operators to customize and extend the dashboard without the need for a custom build which slows down the adoption of new dashboard version.

• [X] Customize appearance (Dashboard Theming) #953 #980
• [x] Custom Cloud Providers
  • [X] Add additional cloud providers via configuration #1434 #1553
  • [x] Add secrets page via configuration #1553
  • [x] Customize built-in vendors #1553
  • [x] Add additional input fields to create cluster page via configuration #1445
• [x] Introduce basic branding functionality #1568

[vlerenc]

@grolu Are more changes planned (just asking because all checkboxes are checked)?

[grolu]

The PR ist still not reviewed. But hopefully we can merge soon... Other than that there are no more changes planned.