Configuration guide naming.field_casing option doesn't exist

[thiagomajesk]

The configuration guide mentions a naming.field_casing option, but this option only works in the root of the configuration default: [field_casing: :snake].

https://github.com/aj-foster/open-api-generator/blob/1a09bae7f6db6ed9f29b3f5dde476e141e4574b0/lib/open_api/processor.ex
https://github.com/aj-foster/open-api-generator/blob/1a09bae7f6db6ed9f29b3f5dde476e141e4574b0/lib/open_api/processor.ex

PS.: I wonder if we can change the default value of this option to snake (I imagine that is what most Elixir users would expect by default).

Update: I also noticed that operations opts keys are not following the defined normalization which is kinda annoying. I'm testing with this spec: https://cloud.langfuse.com/generated/api/openapi.yml and the configuration below:

config :oapi_generator,
    default: [
      field_casing: :snake,
      output: [
        field_casing: :snake,
        base_module: LangfuseSdk.Generated,
        default_client: LangfuseSdk.Support.Client,
        location: "lib/langfuse_sdk",
        operation_subdirectory: "generated/operations/",
        schema_subdirectory: "generated/schemas/"
      ]
    ]