Add additional endpoints support

[avivm]

Add to sidebar "Custom" header with loader.
If not found show "No custom endpoints" with help icon
Add custom endpoint to demo

• Add endpoint to retrieve additional (non-managed, templated: false) endpoints
• Add endpoint to actuator controller accepting a path variable as the endpoint, passthrough to actuator

Frontend:

• Foreach additional endpoint, display in a new category
• Display as a visual JSON

Demo:

• Add custom endpoint with custom information

[Idane]

Current issue with this task:

We can't rely that the href being returned from Actuator is the true URL, meaning we can never get the relative url of the endpoint reliably