fix(quietperiod): Fixup config props (#885)

My change in #784 caused issues for anyone who had the quiet period properties set as I removed the setters
This change fixes that

echo-pipelinetriggers/src/main/java/com/netflix/spinnaker/echo/config/QuietPeriodIndicatorConfigurationProperties.java

@@ -28,7 +28,31 @@
 import org.slf4j.LoggerFactory;
 import org.springframework.boot.context.properties.ConfigurationProperties;
 
-@ConfigurationProperties(prefix = "quiet-period")
+/**
+ * Configuration properties for QuietPeriodIndicator
+ *
+ * <p>CAVEAT: These properties are a bit weird in that they have only one setter (for
+ * suppressedTriggerTypes) This is because all these properties are always queried from the
+ * DynamicConfigService, which will use Spring properties as one of the sources so no setter is
+ * needed. This is also why we include ignoreInvalidFields = true on the annotation below
+ *
+ * <p>The expectation is that quiet period can be changed easily at runtime without re-deploying.
+ *
+ * <p>Example of properties:
+ *
+ * <pre>
+ * quietPeriod:
+ *  enabled: true
+ *  startIso: 2020-02-09T21:00:00Z
+ *  endIso: 2020-02-10T13:00:00Z
+ *  suppressedTriggerTypes:
+ *    - cron
+ *    - docker
+ *    - git
+ *    - jenkins
+ * </pre>
+ */
+@ConfigurationProperties(prefix = "quiet-period", ignoreInvalidFields = true)
 public class QuietPeriodIndicatorConfigurationProperties {
 
   private List<String> suppressedTriggerTypes = new ArrayList<>();