do not escape anything in mustache, test it for preamble

dumpAst/src/main/resources/dumpAst.mustache

 @startuml
 {{#PrintConfig}}
-scale {{Scale}}
+scale {{{Scale}}}
   {{#Headers}}
-{{Value}}
+{{{Value}}}
   {{/Headers}}
 {{/PrintConfig}}
 
 {{#DumpNodes}}
   {{#isAstNode}}
     {{^Invisible}}
-object "{{{labelAndTextColor}}}" as {{name}} {{#backgroundColor}}#{{{backgroundColor}}}{{/backgroundColor}} {
+object "{{{labelAndTextColor}}}" as {{{name}}} {{#backgroundColor}}#{{{backgroundColor}}}{{/backgroundColor}} {
       {{#DumpTokens}}
         {{#isDumpValueToken}}
-  {{label}} = {{{Value}}}
+  {{{label}}} = {{{Value}}}
         {{/isDumpValueToken}}
       {{/DumpTokens}}
 }
@@ -24,7 +24,7 @@ object "{{{labelAndTextColor}}}" as {{name}} {{#backgroundColor}}#{{{backgroundC
   {{#DumpTokens}}
     {{^Invisible}}
       {{^isDumpValueToken}}
-{{outerNodeName}} ..> {{innerNodeName}} : {{label}}
+{{{outerNodeName}}} ..> {{{innerNodeName}}} : {{{label}}}
       {{/isDumpValueToken}}
     {{/Invisible}}
   {{/DumpTokens}}
@@ -32,13 +32,13 @@ object "{{{labelAndTextColor}}}" as {{name}} {{#backgroundColor}}#{{{backgroundC
     {{#isList}}
       {{#InnerDumpNodes}}
         {{#bothVisible}}
-{{outerNodeName}} *-- {{innerNodeName}} : {{label}}
+{{{outerNodeName}}} *-- {{{innerNodeName}}} : {{{label}}}
         {{/bothVisible}}
       {{/InnerDumpNodes}}
     {{/isList}}
     {{^isList}}
       {{#bothVisible}}
-{{outerNodeName}} *-- {{innerNodeName}} : {{label}}
+{{{outerNodeName}}} *-- {{{innerNodeName}}} : {{{label}}}
       {{/bothVisible}}
     {{/isList}}
   {{/DumpChildNodes}}
@@ -46,27 +46,27 @@ object "{{{labelAndTextColor}}}" as {{name}} {{#backgroundColor}}#{{{backgroundC
     {{#isList}}
       {{#InnerDumpNodes}}
         {{#bothVisible}}
-{{outerNodeName}} {{#Bidirectional}}<{{/Bidirectional}}--> {{innerNodeName}} : {{label}}
+{{{outerNodeName}}} {{#Bidirectional}}<{{/Bidirectional}}--> {{{innerNodeName}}} : {{{label}}}
         {{/bothVisible}}
       {{/InnerDumpNodes}}
     {{/isList}}
     {{^isList}}
       {{#bothVisible}}
-{{outerNodeName}} {{#Bidirectional}}<{{/Bidirectional}}--> {{innerNodeName}} : {{label}}
+{{{outerNodeName}}} {{#Bidirectional}}<{{/Bidirectional}}--> {{{innerNodeName}}} : {{{label}}}
       {{/bothVisible}}
     {{/isList}}
   {{/DumpRelations}}
   {{^Invisible}}
     {{#InvisiblePath}}
       {{#InnerDumpNodes}}
-{{outerNodeName}} o.. {{innerNodeName}}
+{{{outerNodeName}}} o.. {{{innerNodeName}}}
       {{/InnerDumpNodes}}
     {{/InvisiblePath}}
   {{/Invisible}}
   {{#PrintConfig}}{{#orderChildren}}
       {{#myChildren}}
           {{#hasSuccessor}}
-{{name}} -[hidden]right-> {{#successor}}{{name}}{{/successor}}
+{{{name}}} -[hidden]right-> {{#successor}}{{{name}}}{{/successor}}
           {{/hasSuccessor}}
       {{/myChildren}}
   {{/orderChildren}}{{/PrintConfig}}
@@ -75,7 +75,7 @@ object "{{{labelAndTextColor}}}" as {{name}} {{#backgroundColor}}#{{{backgroundC
   {{#Debug}}
 legend right
   %date()
-  dumpAst: {{version}}
+  dumpAst: {{{version}}}
   plantuml: %version()
 endlegend
   {{/Debug}}

testDumper/src/test/java/de/tudresden/inf/st/jastadd/testDumper/TestSimple.java

@@ -28,6 +28,17 @@ public class TestSimple {
     assertEquals(0, actualRoot.getNumDumpRelation());
   }
 
+  @Test
+  public void testCustomPreamble() {
+    Root root = createRoot(null, null);
+    String preamble = "{<\n>\n}";
+    ExposingDumpBuilder builder = new ExposingDumpBuilder(root);
+    builder.excludeNullNodes().customPreamble(preamble);
+    DumpAst dumpAst = builder.build();
+    String puml = dumpAst.toPlantUml();
+    assertThat(puml).contains(preamble);
+  }
+
   @Test void testChildlessNonterminal() {
     Root root = createRoot(createA(A_NAME, a -> a.setD(new D())), null);
     List<DumpNode> nodes = TestUtils.dumpModel(root);