code: public FixedDelayBuilder<RetryBuilder<P>> fixedDelay() {
  		if (fixedDelay == null) {
  			fixedDelay = new FixedDelayBuilder<>(this, environmentBuilder);
  		}
  		return fixedDelay;
  	}
docs: Retry several times with a fixed delay between each try until the maximum
  attempts is reached.
  
  For example:
  
  <pre>
  .fixedDelay()
  .delay(500)
  .maxRetries(5)
  </pre>
  
  Means that a retry will be attempted every 500ms until 5 attempts are
  reached (inclusive). For example, you want to connect to an external
  system at t1=0 and the connection timeout (100ms) is triggered at
  t2=100ms. Using this retry will provide the following behavior:
  
  <ul>
  <li>0: connect</li>
  <li>100: timeout</li>
  <li>600: connect</li>
  <li>700: timeout</li>
  <li>1200: connect</li>
  <li>1300: timeout</li>
  <li>1800: connect</li>
  <li>1900: timeout</li>
  <li>2400: connect</li>
  <li>2500: timeout</li>
  <li>3000: connect</li>
  <li>3100: timeout</li>
  <li>fail</li>
  </ul>
  
  @return the builder to configure retry delay and maximum attempts