Improve IndexConfig derive macro

[funlennysub]

Pull Request

Related issue

None

What does this PR do?

• A way to override the index name
• A way to change pagination settings
• Minor code improvements

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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)?
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[funlennysub]

Perhaps if there's no fields with displayed flag, it should default to "*" as meilisearch does, because from my understanding right now it will just set it to an empty array?