Derive Macro ResponseModelAliases 

#[derive(ResponseModelAliases)]
{
    // Attributes available to this derive:
    #[serde]
}

Derive response model alias metadata for FastAPI-compatible by_alias handling.

This emits an implementation of fastapi_core::ResponseModelAliases using #[serde(rename = ...)] and #[serde(rename_all = ...)] attributes.