Revert "Remove deprecated constant META_FIELDS_BEFORE_7DOT8 (#13860)" (#13916)

* Revert "Remove deprecated constant META_FIELDS_BEFORE_7DOT8 (#13860)"

This reverts commit 9832972.

* Update CHANGELOG-3.0

Signed-off-by: Craig Perkins <cwperx@amazon.com>

---------

Signed-off-by: Craig Perkins <cwperx@amazon.com>

Author: cwperks

CHANGELOG-3.0.md

@@ -24,7 +24,6 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Add task completion count in search backpressure stats API ([#10028](https://github.com/opensearch-project/OpenSearch/pull/10028/))
 - Deprecate CamelCase `PathHierarchy` tokenizer name in favor to lowercase `path_hierarchy` ([#10894](https://github.com/opensearch-project/OpenSearch/pull/10894))
 - Breaking change: Do not request "search_pipelines" metrics by default in NodesInfoRequest ([#12497](https://github.com/opensearch-project/OpenSearch/pull/12497))
-- Remove deprecated constant META_FIELDS_BEFORE_7DOT8 ([#13860](https://github.com/opensearch-project/OpenSearch/pull/13860))
 
 ### Deprecated
 

server/src/main/java/org/opensearch/index/mapper/MapperService.java

@@ -73,6 +73,7 @@
 import java.io.Closeable;
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -200,6 +201,11 @@ public enum MergeReason {
         Property.IndexScope,
         Property.Deprecated
     );
+    // Deprecated set of meta-fields, for checking if a field is meta, use an instance method isMetadataField instead
+    @Deprecated
+    public static final Set<String> META_FIELDS_BEFORE_7DOT8 = Collections.unmodifiableSet(
+        new HashSet<>(Arrays.asList("_id", IgnoredFieldMapper.NAME, "_index", "_routing", "_size", "_timestamp", "_ttl", "_type"))
+    );
 
     private static final DeprecationLogger deprecationLogger = DeprecationLogger.getLogger(MapperService.class);