Added javadoc.

Signed-off-by: Kai Zimmermann <kai.zimmermann@bosch-si.com>

hawkbit-core/src/main/java/org/eclipse/hawkbit/tenancy/configuration/DurationHelper.java

@@ -36,6 +36,13 @@ public final class DurationHelper {
             this.max = max;
         }
 
+        /**
+         * Checks if the requested duration is in the defined min/max range.
+         * 
+         * @param duration
+         *            to checked
+         * @return <code>true</code> if in time range
+         */
         public boolean isWithinRange(final Duration duration) {
             return duration.compareTo(min) >= 0 && duration.compareTo(max) <= 0;
         }