added proper types for facetStats, facetDistributions and matchesPosition

[ahmednfwela]

Pull Request

Related issue

Fixes #294

What does this PR do?

• Introduces new classes
  1. FacetStat
  2. MatchPosition
• [Breaking] change Searchable<T> to have proper types:

  - final Object? facetDistribution;
  + final Map<String, Map<String, int>>? facetDistribution;
  - final Object? matchesPosition;    
  + final Map<String, List<MatchPosition>>? matchesPosition;
  + final Map<String, FacetStat>? facetStats;

• Internal refactoring to not repeat any deserialization logic between Searchable<T> and its subclasses SearchResult<T> and PaginatedSearchResult<T>

PR checklist

Please check if your PR fulfills the following requirements:

• Does this PR fix an existing issue, or have you listed the changes applied in the PR description (and why they are needed)?
• Have you read the contributing guidelines?
• Have you made sure that the title is accurate and descriptive of the changes?

Thank you so much for contributing to Meilisearch!

cc @brunoocasali

[brunoocasali]

Thanks a lot for the detailed PR description. It is extremely useful to me! 🥇

I left some comments. If you agree with them we can apply them to the entire repo.

[brunoocasali]

Thanks @ahmednfwela 🥇

bors merge

[bors]

Build succeeded:

• integration-tests (dart 2.15.1)
• integration-tests (dart 2.19.0)
• linter-check
• pana