Generic IntoParameter on enum with value_type

[irevoire]

Hey,

I'm coming back to integrate this awesome lib in @meilisearch; I see there have been a lot of changes since the last time I used it 🎉

I was wondering if there was a way to make that work:

/// A type representing the content of a query parameter that can either not exist, be equal to a star (*), or represent a list of other values
#[derive(Debug, Default, Clone, IntoParams)]
#[into_params(value_type = Option<Vec<T>>)]
pub enum OptionStarOrList<T> {
    #[default]
    None,
    Star,
    List(Vec<T>),
}

Context

Maybe it's the wrong thing to do, though; let me know if you have a better idea!
We use this type a lot in Meilisearch.
It's a query parameter that can be used like that:

• Not mandatory; it's not specified /tasks
• You use it with one value `/tasks?uid=3
• You use it with multiple values /tasks?uid=3,4,5
• Or you can use it with a star to match everything: /tasks?uid=*

[Jeadie]

We have same issue with spiceai/spiceai. From what I can see, answer is no, but IntoParams can be manually implemented. This PR has an example: #680

Have not verified myself.