move scatter plot creation into an AggregateHandler

pdb-ui/src/main/java/org/lucares/pdbui/PlotSettingsTransformer.java

@@ -5,6 +5,7 @@ import org.lucares.pdb.plot.api.NullAggregate;
 import org.lucares.pdb.plot.api.ParallelRequestsAggregate;
 import org.lucares.pdb.plot.api.CumulativeDistributionHandler;
 import org.lucares.pdb.plot.api.PlotSettings;
+import org.lucares.pdb.plot.api.ScatterAggregateHandler;
 import org.lucares.pdb.plot.api.TimeRangeUnitInternal;
 import org.lucares.pdbui.domain.Aggregate;
 import org.lucares.pdbui.domain.PlotRequest;
@@ -61,6 +62,8 @@ class PlotSettingsTransformer {
 			return new CumulativeDistributionHandler();
 		case PARALLEL:
 			return new ParallelRequestsAggregate();
+		case SCATTER:
+		  return new ScatterAggregateHandler();
 		}
 		throw new IllegalStateException("unhandled enum: " + aggregate);
 	}

pdb-ui/src/main/java/org/lucares/pdbui/domain/Aggregate.java

@@ -1,14 +1,19 @@
 package org.lucares.pdbui.domain;
 
+/**
+ * Note: The order in this enum defines the order in which the aggregates are drawn.
+ */
 public enum Aggregate {
 	NONE,
 
+	PARALLEL,
+	
+	SCATTER,
+	
 	/**
 	 * Empirical cumulative distribution functions
 	 *
 	 * @see https://serialmentor.com/dataviz/ecdf-qq.html
 	 */
 	CUM_DISTRIBUTION,
-
-	PARALLEL
 }