Reject unknown fields from API requests

[noyoshi]

Feature request

We should reject requests that contain unknown fields

Motivation

This can help users debug why prompts aren't working right - its much easier if the server says "validation error" when you forget to set the API token in the "parameters" section of the request, for instance, and instead set it at the top level. Otherwise, you can get confusing errors such as "access denied" which makes no sense.

Your contribution

Can add https://serde.rs/container-attrs.html#deny_unknown_fields annotation to all of the requests