[SOLR-17185] Open ValueAugmenter in ValueAugmenterFactory for extension (#2315)

* Open value augmenter for extension

* [SOLR-17185] add public compile test

* [SOLR-17185] change visibility of fields

* [SOLR-17185] add license file // tidy

Author: tboeghk

solr/core/src/java/org/apache/solr/response/transform/ValueAugmenterFactory.java

@@ -72,9 +72,9 @@ public DocTransformer create(String field, SolrParams params, SolrQueryRequest r
     return new ValueAugmenter(field, val);
   }
 
-  static class ValueAugmenter extends DocTransformer {
-    final String name;
-    final Object value;
+  public static class ValueAugmenter extends DocTransformer {
+    private final String name;
+    protected final Object value;
 
     public ValueAugmenter(String name, Object value) {
       this.name = name;

solr/core/src/test/org/apache/solr/pkg/ValueAugmenterPublicTest.java

@@ -0,0 +1,29 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.solr.pkg;
+
+import org.apache.solr.response.transform.ValueAugmenterFactory;
+import org.junit.Test;
+
+public class ValueAugmenterPublicTest {
+
+  @Test
+  public void testValueAugmenterIsOpenForExtension() {
+    // this should compile from this package
+    new ValueAugmenterFactory.ValueAugmenter("bee_sI", new Object());
+  }
+}