Add reasoning output

Problem/Motivation

This issue currently is not to integrate Mistral with #3546573: Add normalization for getting reasoning text, but to have an example of this. Since we use Chat Completion on most other providers we can't actually get the reasoning blocks, so because of this we use a modified version of this and the client. Patches needed as well.

Steps to reproduce

Proposed resolution

Install this together with #3546573: Add normalization for getting reasoning text and use API Explorer to test it.

Remaining tasks

User interface changes

API changes

Data model changes