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

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)?
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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?

[CommanderStorm]

(not a maintainer)

Since this change is quite sublte otherwise: could you add a doc comment explaining how the macro can be used?

A testcase would obviously also be nice, but since this was not tested beforehand..

[Mubelotix]

Hello @funlennysub, thank you for your contribution! Giving the ability to change the index name definitely seems useful. However, I don't see what makes max_total_hits any different than all the other settings. If we support max_total_hits, that would leave the door open to every single other setting and I don't want this macro to become a multi-thousand line macro.

Could you just keep the way to set the index name please?