Merge #716

716: Add support for conversational search r=curquiza a=kumarUjjawal

# Pull Request


## Related issue
Fixes #696

## What does this PR do?


## PR checklist
Please check if your PR fulfills the following requirements:
- [x] Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
- [x] Have you read the contributing guidelines?
- [x] Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!


<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

* **New Features**
  * Chat workspaces management: list (with pagination), retrieve, and view/update/reset workspace settings.
  * Configurable prompts included in workspace settings with builder-style configuration.
  * Optional streaming API for real-time chat completions.

* **Documentation**
  * Added introductory documentation for the new chats module.

* **Tests**
  * Integration test covering full chat workspace lifecycle (list, retrieve, configure prompts, update/reset).

* **Chores**
  * Added a crate-private accessor for the HTTP client used by the optional reqwest integration.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: Kumar Ujjawal <ujjawalpathak6@gmail.com>
Co-authored-by: Clémentine <clementine@meilisearch.com>

Author: 3 people