fix: serialize data before sending it to the backend

[mochetts]

Description 📖

This pull request fixes the inertia client so that it serializes data, using deepConvertKeys(data, snakeCase) before sending it to the backend. This is the same behavior as the standard js_from_routes client.

Background 📜

This was happening because the data serialization / deserialization is completely missing for the inertia client. This causes a mismatch between the rails backend and the frontend as when submitting data to the rails app, it's expecting snake_case params but the inertia client is sending camelCase params.

_Image: the expected param is tax_id in the backend, but the frontend is sending taxId_

The Fix 🔨

By using the same convention as for the standard client, in which we have a Config object that takes a serializeData function that gets called before sending data to the backend, we can deepConvertKeys with snakeCase in order to send the right key casing to the backend.

Future Work 🔮

It could be also good to implement the rest of the configuration options (e.g deserializeData, baseUrl, etc). I didn't implement the deserializeData because I'm using types_from_serializers which already sends the data in camelCase format to the frontend. So no need for deserialization.

[mochetts]

This can be better solved by adding a before_action hook in the rails application controller:

class ApplicationController < ActionController::Base

  before_action :deep_transform_params

  # Underscore params keys as they come camelized from the frontend
  def deep_transform_params
    params.merge!(params.to_unsafe_h.deep_transform_keys(&:underscore))
  end
end

This way we don't hijack the inertia transform that can only be used once (cannot stack transforms)