Pull Request

Related issue

Fixes #609

What does this PR do?

This PR adds types and methods to use the federated multi search API. There are multiple ways to add this to this library, depending on how strictly one wants to type everything. I decided to:

• Add a new FederatedMultiSearchResponse, which also required a new Client::execute_federated_multi_search_query. The response of federated searches is just very different from normal multi searches, and I didn't think having an enum returned by execute_multi_search_query was a particularly nice design (and it would have been a breaking change).
• Add a federation: Option<FederationHitInfo> to each SearchResult (which is None for non-federated searches). I don't think it's worth to have a dedicated FederatedSearchResult.
• Add MultiSearchQuery::with_federation which returns a new FederatedMultiSearchQuery. One could also change MultiSearchQuery to be able to represent federated queries, but I had a slight preference for my solution.

PR checklist

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• Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
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Thank you so much for contributing to Meilisearch!