Fix grade calculator being serialized (#59)

The new calculator that's based on templates has a reference to the @Entity for the template which should not be serialized.

Fixes #40

## How to test/replicate
1. Log in as a supervisor
1. Open a project that's new enough to use a grading report template with grade limits
1. Go to the "Finishing up" tab
1. Go to the sub-tab for an individual author

Reviewed-on: #59
Reviewed-by: Nico Athanassiadis <nico@dsv.su.se>
Co-authored-by: Andreas Svanberg <andreass@dsv.su.se>
Co-committed-by: Andreas Svanberg <andreass@dsv.su.se>

core/src/main/java/se/su/dsv/scipro/report/GradeCalculator.java

@@ -1,8 +1,6 @@
 package se.su.dsv.scipro.report;
 
-import java.io.Serializable;
+public interface GradeCalculator {
-
-public interface GradeCalculator extends Serializable {
     GradingReport.Grade getGrade(GradingReport gradingReport);
 
     long getPoints(GradingReport gradingReport);

view/src/main/java/se/su/dsv/scipro/grading/GradingReportPointsPanel.java

@@ -4,7 +4,6 @@ import org.apache.wicket.markup.html.WebMarkupContainer;
 import org.apache.wicket.markup.html.basic.Label;
 import org.apache.wicket.markup.html.panel.Panel;
 import org.apache.wicket.model.IModel;
-import org.apache.wicket.model.LoadableDetachableModel;
 import se.su.dsv.scipro.components.OppositeVisibility;
 import se.su.dsv.scipro.report.GradeCalculator;
 import se.su.dsv.scipro.report.GradingReport;
@@ -18,15 +17,13 @@ public class GradingReportPointsPanel extends Panel {
     public GradingReportPointsPanel(
         String id,
         final IModel<? extends GradingReport> gradingReportIModel,
-        final GradeCalculator gradeCalculator
+        final IModel<GradeCalculator> gradeCalculator
     ) {
         super(id, gradingReportIModel);
-        final IModel<GradingReport.Grade> gradeModel = new LoadableDetachableModel<>() {
+        final IModel<GradingReport.Grade> gradeModel = gradingReportIModel.combineWith(
-            @Override
+            gradeCalculator,
-            protected GradingReport.Grade load() {
+            GradingReport::getGrade
-                return gradingReportIModel.getObject().getGrade(gradeCalculator);
+        );
-            }
-        };
         final Label grade = new Label(GRADE, gradeModel.map(GradingReport.Grade::name)) {
             @Override
             protected void onConfigure() {
@@ -36,12 +33,7 @@ public class GradingReportPointsPanel extends Panel {
         };
         add(grade);
 
-        final IModel<Long> points = new LoadableDetachableModel<>() {
+        final IModel<Long> points = gradingReportIModel.combineWith(gradeCalculator, GradingReport::getPoints);
-            @Override
-            protected Long load() {
-                return gradingReportIModel.getObject().getPoints(gradeCalculator);
-            }
-        };
         add(new Label(POINTS_LABEL, points));
 
         add(new WebMarkupContainer(NO_GRADE_EXPLANATION).add(new OppositeVisibility(grade)));

view/src/main/java/se/su/dsv/scipro/grading/IndividualAuthorAssessmentPanel.java

@@ -271,8 +271,8 @@ public class IndividualAuthorAssessmentPanel extends GenericPanel<User> {
                 new TemplatePanel("points_to_grade_conversion", gradingReport.map(SupervisorGradingReport::getProject))
             );
 
-            GradeCalculator supervisorCalculator = gradeCalculatorService.getSupervisorCalculator(
+            IModel<GradeCalculator> supervisorCalculator = LoadableDetachableModel.of(() ->
-                gradingReport.getObject().getProject()
+                gradeCalculatorService.getSupervisorCalculator(gradingReport.getObject().getProject())
             );
             add(new GradingReportPointsPanel("points", gradingReport, supervisorCalculator));
 

view/src/test/java/se/su/dsv/scipro/grading/GradingReportPointsPanelTest.java

@@ -62,7 +62,7 @@ public class GradingReportPointsPanelTest extends SciProTest {
 
     private void startPanel() {
         panel = tester.startComponentInPage(
-            new GradingReportPointsPanel("id", Model.of(gradingReport), gradeCalculator)
+            new GradingReportPointsPanel("id", Model.of(gradingReport), () -> gradeCalculator)
         );
     }