Update in javadocs for DerivedFieldSupportedTypes and DerivedFieldType

Signed-off-by: Rishabh Maurya <rishabhmaurya05@gmail.com>

Author: rishabhmaurya

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

@@ -31,6 +31,11 @@
 import java.util.function.Function;
 import java.util.stream.Collectors;
 
+/**
+ * Contains logic to get the FieldMapper for a given type of derived field. Also, for a given type of derived field,
+ * it is used to create an IndexableField for the provided type and object. It is useful when indexing into
+ * lucene MemoryIndex in {@link org.opensearch.index.query.DerivedFieldQuery}.
+ */
 enum DerivedFieldSupportedTypes {
 
     BOOLEAN("boolean", (name, context) -> {

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

@@ -33,7 +33,7 @@
 
 /**
  * MappedFieldType for Derived Fields
- * Contains logic to different type of queries on derived fields
+ * Contains logic to execute different type of queries on a derived field of given type.
  * @opensearch.internal
  */
 public final class DerivedFieldType extends MappedFieldType {