fix: apply integer type fitting in lib.rs

[holdeg]

We already have logic in postProcessModelProperty to fit integer parameters into the correct Rust primitives. However, this doesn't apply to CodegenParameters so integer-typed parameters which end up in function calls for Api traits in lib.rs are always i32, even when this is improper.

This commit refactors integer type fitting so that we can run it on both CodegenParameter and model post-processing.

Testing

I've included a new RustServerCodegenTest file and an integer-params.yaml test case to cover the new function (and also checked this locally against the API definition which prompted me to contribute this).

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---

Summary by cubic

Fixes integer parameter types in the Rust server generator so API trait, client, and server signatures use the correct Rust integer size and signedness instead of defaulting to i32. Applies integer fitting based on format and min/max to both parameters and model properties, and updates samples.

• Bug Fixes

  • Apply integer type fitting to CodegenParameter so generated lib.rs, client, and server use the right Rust integer (including unsigned) rather than i32.
  • Update petstore samples (e.g., integer/int32 -> u32, order_id -> u64).

• Refactors

  • Extract applyIntegerTypeFitting and reuse for parameters and properties; supports int32/int64/uint32/uint64 and min/max constraints.
  • Add a focused test and spec to assert fitted types in lib.rs.

^{Written for commit a8fe886. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 9 files

[wing328]

https://github.com/OpenAPITools/openapi-generator/actions/runs/21522482250/job/62087333292?pr=22853

thanks for the PR

please review the build failure when you've time

[wing328]

cc @frol (2017/07) @farcaller (2017/08) @richardwhiuk (2019/07) @paladinzh (2020/05) @jacob-pro (2022/10) @dsteeley (2025/07)