multipart.rb

f01x = ENV['FARADAY_VERSION'] == '0.1x'

if f01x
  puts 'loading faraday v0.17.x...'
  require 'rubygems'
  gem 'faraday', '~> 0.17.0'
else
  puts 'loading latest faraday...'
end

require 'faraday'
require 'json'
puts Faraday::VERSION

BASE_URL = 'https://requestbin.io/17vs3fa1'

client = Faraday::Connection.new(url: BASE_URL) do |builder|
  #builder.request :cookie_jar
  builder.request :multipart
  builder.request :url_encoded
  builder.adapter :net_http
end

message = {title: "title", body: "body of message", recipientIdList:[186554]}
payload = if f01x
  { message: Faraday::UploadIO.new(StringIO.new(JSON.dump(message)), 'application/json') }
else
  { message: Faraday::ParamPart.new(JSON.dump(message), 'application/json') }
end

response = client.post(BASE_URL) do |request|
  request.headers['Content-Type'] = 'multipart/form-data'
  request.body = payload
end

puts response.status
puts response.body