Ability to pass error messages from API to UI

[nenb]

Feature description

The ability to pass any error message that is raised in the API to the UI. Currently this is not possible as StreamingResponse is used which results in peer closed connection without sending complete message body being raised in the UI for all API errors.

Value and/or benefit

Better user experience eg ability to determine more easily whether an issue is UI or API-related.

Anything else?

No response