title: Sinatra not passing header with redirect
body: <p>I have a simple Sinatra proxy, which when an endpoint is called, will redirect to another endpoint on the same Sinatra proxy. </p>
  
  <p>When I make a request with a header, the proxy doesn't seem to pass this header through to the second endpoint when the request redirects in the first. This is my code:</p>
  
  <pre><code>    get '/first' do 
          # get the header from the request
        username = env['HTTP_USERNAME'] 
          # set the header for the response
        response['username'] = username 
        redirect '/second'
      end
  
      get '/second' do 
          # This doesn't exist when redirected from /first
      puts env['HTTP_USERNAME']
  
          # Here is a list of all headers
        env.each_key do |key|
          puts "KEY: #{key}  VALUE: #{env[key]}" unless key.nil?
        end
  
        "DONE"
      end
  </code></pre>
  
  <p>Any tips would be greatly appreciated.</p>
  
  <p>Thanks</p>