app.rb

# frozen_string_literal: true

require 'sinatra'
require 'sinatra/reloader'
require 'sinatra/json'

post '/images' do
  image = {name: 'i_like_dog_very_much', url: 'https://example.com/image.png'}
  # p request

  json image
end

# bundle install --path vendor/bundle
# bundle exec ruby app.rb
# POST http:locahost:4567/images