How to send multipart and json requests to Google Drive API using Ruby's HTTParty

api_send_json_response.rb

class DriveAPI
  include HTTParty
  base_uri 'https://www.googleapis.com'
  #for debugging
  debug_output $stdout
end

def create_file(file_name, parent_id)
    check_token!
    access_token = current_user.access_token

    response = DriveAPI.post(
                  '/drive/v3/files',
                  :body => {  "mimeType"=> "application/vnd.google-apps.document",
                              "name"=> "#{file_name}",
                              "parents"=> ["#{parent_id}"]
                           }.to_json,
                  :headers => {
                          "Authorization" => "Bearer #{access_token}",
                          "Content-Type" => "application/json"
                  }
               )
    response
  end

api_send_multipart.rb

class DriveAPI
  include HTTParty
  base_uri 'https://www.googleapis.com'
  #for debugging
  debug_output $stdout
end

#creates a Google document
def upload_file(file_name="xyzabc", parent_id, html)
  check_token!
  access_token = current_user.access_token

  json = {  "mimeType"=> "application/vnd.google-apps.document",
              "name"=> "#{file_name}",
              "parents"=> ["#{parent_id}"]
           }.to_json

  #Compose multipart body
  @boundary = "AaB03x"
  post_body = []
  post_body << "--#{@boundary}\r\n"
  post_body << "Content-Type: application/json"
  post_body << "\r\n\r\n"
  post_body << json
  post_body << "\r\n--#{@boundary}\r\n"
  post_body << "Content-Type: text/html"
  post_body << "\r\n\r\n"
  post_body << html
  post_body << "\r\n--#{@boundary}--\r\n"
  body = post_body.join

  response = DriveAPI.post(
                '/upload/drive/v3/files?uploadType=multipart',
                :body => body,
                :headers => {
                        "Authorization" => "Bearer #{access_token}",
                        "Content-Type" => "multipart/related; boundary=#{@boundary}"
                }
             )
  response
end