Fix failing build issue in PR on JDK15

Author: oliemansm

build.gradle

@@ -37,6 +37,10 @@ sonarqube {
     }
 }
 
+jacoco {
+    toolVersion = "0.8.7.202012290703"
+}
+
 subprojects {
     apply plugin: 'idea'
     apply plugin: 'jacoco'

graphiql-spring-boot-autoconfigure/src/main/java/graphql/kickstart/graphiql/boot/GraphiQLProperties.java

@@ -32,12 +32,27 @@ static class CodeMirror {
   @Data
   static class Props {
 
-    private Variables variables = new Variables();
+    private GraphiQLVariables variables = new GraphiQLVariables();
 
+    /**
+     * See https://github.com/graphql/graphiql/tree/main/packages/graphiql#props
+     */
     @Data
-    static class Variables {
+    static class GraphiQLVariables {
 
+      private String query;
+      private String variables;
+      private String headers;
+      private String operationName;
+      private String response;
+      private String defaultQuery;
+      private boolean defaultVariableEditorOpen;
+      private boolean defaultSecondaryEditorOpen;
       private String editorTheme;
+      private boolean readOnly;
+      private boolean docsExplorerOpen;
+      private boolean headerEditorEnabled;
+      private boolean shouldPersistHeaders;
     }
   }