title: In Gatling: How can I inject two scenarios concurrently while changing injection properties throughout the test?
body: <p>My simulation runs two concurrent scenarios, one ramps up to 1000 users and iterates the scenario flow throughout the whole test duration
  while the second one injects 500 users every hour for 10 minutes. I am doing this to simulate a peak every hour. </p>
  
  <p>The simulation looks more or less as the following:</p>
  
  <pre><code>setUp(steadyStateScenario.inject(rampConcurrentUsers(1) to (numberOfTestUsers) during (Config.rampUpDuration minutes))
    .protocols(httpconf),
    peakScenario.inject(nothingFor(60 minutes), rampUsers(numberOfPeakTestUsers) during (Config.PeakRampUpDuration minutes))
    .protocols(httpconf))
    .maxDuration(Config.scenarioDuration hours)
    .assertions(global.successfulRequests.percent.is(100))
  </code></pre>
  
  <p>My issue with the current simulation is that I am unable to randomise peak duration and number of peak users.
  To overcome this I would like to execute peakScenario.inject every hour and change values in numberOfPeakTestUsers and Config.PeakRampUpDuration each time it 
  is executed. This should be done while steadyStateScenario is running at the background without interruption. Is that possible?</p>
  
  <p>Cheers. </p>