title: Configuration of a JUnit 5 extension
body: <p>I am upgrading an internal tool based on JUnit 4 to JUnit 5. Therefore I have to write an extension for the test execution. The task of the extension should be to ensure the correct state of external application (start it if it is not running etc.). To perform this task serveral parameter (from the commandline) are needed. </p>
  
  <p>Can I store these parameters in the extension context? And if so, how can I access it before the actual tests run starts?</p>