Explain which config values should be mounted from secrets, not configmaps

[Cali0707]

[Latent] IIUC the value here is an actual secret (sensitive data). Somewhere it would be worth calling out that, when standing up the MCP server in a cluster, when configs contain sensitive data, they should be mounted from Secrets rather than ConfigMaps.

And some kind of visual indicator in the table for such fields would be nice.

Originally posted by @2uasimojo in #1401 (comment)