Feat: use inner <T as ToTypesenseField>::to_typesense_type() of Vec<T> in derive

[milesgranger]

Change Summary

Deriving Typesense on a struct with a Vec<MyLocalType> field only compiles if MyLocalType: Document (giving "object[]") or is a built-in primitive. And we cannot do impl ToTypesenseField for Vec<MyLocalType> in downstream crates, so requires the #[typesense(type = "...")] per-field work around.

This PR mirrors what build_regular_field already does for flatten: peel Vec<_> (and Vec<Option<_>>) in the proc-macro, resolve ToTypesenseField on the inner type, and append "[]". Downstream crates now only need MyLocalType: ToTypesenseField.

Example that compiles after this PR but not before:

 use serde::{Serialize, Deserialize};                                      
 use typesense::{Typesense, prelude::ToTypesenseField};  
                                                                           
 #[derive(Serialize, Deserialize)]                       
 pub enum Priority { Low, Medium, High }                                   
                                                                           
 impl ToTypesenseField for Priority {
     fn to_typesense_type() -> &'static str { "string" }                   
 }                                                                         

 #[derive(Typesense, Serialize, Deserialize)]                              
 struct Task {                                           
     priority: Priority,        // "string"      (worked before)           
     status: Option<Priority>,  // "string"      (worked before)
     tags: Vec<Priority>,       // "string[]"    (NEW: required #[typesense(type = "string[]")] before)                                   
 }                                                                         

PR Checklist

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[RoDmitry]

Nice solution 👍
I have removed extra ToTypesenseField implementations, and added tests. Tell me if it looks good, and check if it compiles for your code.

[milesgranger]

Super! Yes, looks good and things are still happy on my side. :)
Thank you!