refactor! Formally mark that xxxHandler classes are @internal

End-users are not expected to reference these classes directly. If users want to
customise handling for a particular operation, they should implement the interface
and/or extend from the abstract base class.

Author: acoulton

src/operations/handlers/AddHandler.php

@@ -5,6 +5,9 @@
 use blancks\JsonPatch\json\accessors\UndefinedValue;
 use blancks\JsonPatch\operations\PatchOperation;
 
+/**
+ * @internal
+ */
 final class AddHandler extends PatchOperation
 {
     private mixed $previous;

src/operations/handlers/CopyHandler.php

@@ -5,6 +5,9 @@
 use blancks\JsonPatch\json\accessors\UndefinedValue;
 use blancks\JsonPatch\operations\PatchOperation;
 
+/**
+ * @internal
+ */
 final class CopyHandler extends PatchOperation
 {
     private mixed $previous;

src/operations/handlers/MoveHandler.php

@@ -4,6 +4,9 @@
 
 use blancks\JsonPatch\operations\PatchOperation;
 
+/**
+ * @internal
+ */
 final class MoveHandler extends PatchOperation
 {
     /**

src/operations/handlers/RemoveHandler.php

@@ -4,6 +4,9 @@
 
 use blancks\JsonPatch\operations\PatchOperation;
 
+/**
+ * @internal
+ */
 final class RemoveHandler extends PatchOperation
 {
     private mixed $previous;

src/operations/handlers/ReplaceHandler.php

@@ -4,6 +4,9 @@
 
 use blancks\JsonPatch\operations\PatchOperation;
 
+/**
+ * @internal
+ */
 final class ReplaceHandler extends PatchOperation
 {
     private mixed $previous;

src/operations/handlers/TestHandler.php

@@ -5,6 +5,9 @@
 use blancks\JsonPatch\exceptions\FailedTestException;
 use blancks\JsonPatch\operations\PatchOperation;
 
+/**
+ * @internal
+ */
 final class TestHandler extends PatchOperation
 {
     /**