[OpenAPI] Support `multipart/form-data` params in the `@param` tag

Description

Currently, the @param tag in Rage::OpenAPI only supports documenting query parameters. However, when an endpoint accepts file uploads via multipart/form-data, there is no way to document these parameters using the existing tag.

The goal of this issue is to update the @param tag to support multipart/form-data parameters, so that file upload endpoints can be properly documented in the generated OpenAPI specification.

For example, given an endpoint like this:

class Api::V1::PhotosController < ApplicationController
  # @param image {File} The photo to upload
  # @param caption? {String} An optional caption for the photo
  def create
  end
end

The generated OpenAPI specification should include a multipart/form-data request body with the correct schema, e.g.:

requestBody:
  content:
    multipart/form-data:
      schema:
        type: object
        properties:
          image:
            type: string
            format: binary
          caption:
            type: string
        required:
          - image

Tips

• Check the OpenAPI docs to understand how @param and @request tags currently work.
• Review how the OpenAPI specification describes file uploads.
• The implementation will likely need to detect File (or a similar type) in the @param tag and generate a multipart/form-data request body instead of a query parameter.
• You can keep the first iteration intentionally narrow:
  • only multipart/form-data
  • only file -> {type: "string", format: "binary"}
• Check the architecture doc that shows how Rage's core components interact with each other and outlines the design principles.
• Feel free to ask any questions or request help in the comments below!