[adp] MCP docs feedback

[simon0191]

1. It'd be great if we can include screenshots for the most important flows like oauth client and provider creation, MCP configuration, and MCP testing
2. It'd be great to replace the arch diagrams in ascci for something better like a mermaid diagram, or something else.
3. It'd be great if in all the configuration steps we show how to do it in the UI, with the API, and with rpk