pass the add flag to the array callback for json_patch copy

tests/json_patch_tests.json

@@ -386,6 +386,11 @@
       "expected": {"foo": [null, null]},
       "comment": "null value should be valid array element to be copied" },
 
+    { "doc": {"foo": [1, 2, 3]},
+      "patch": [{"op": "copy", "from": "/foo/0", "path": "/foo/1"}],
+      "expected": {"foo": [1, 1, 2, 3]},
+      "comment": "copy to an array index inserts, it does not replace" },
+
     { "doc": {"foo": [null, 1]},
       "patch": [{"op": "remove", "path": "/foo/0"}],
       "expected": {"foo": [1]},

tests/test_json_patch.expected

@@ -117,6 +117,7 @@ Testing 'null value should be valid array element', doc '{ "foo": [ null ] }' pa
 Testing 'null value should be valid array element to be replaced with something truthy', doc '{ "foo": [ null ] }' patch '[ { "op": "replace", "path": "\/foo\/0", "value": "truthy" } ]' : OK
 Testing 'null value should be valid array element to be moved', doc '{ "foo": [ null, 1 ] }' patch '[ { "op": "move", "from": "\/foo\/0", "path": "\/bar" } ]' : OK
 Testing 'null value should be valid array element to be copied', doc '{ "foo": [ null ] }' patch '[ { "op": "copy", "from": "\/foo\/0", "path": "\/foo\/-" } ]' : OK
+Testing 'copy to an array index inserts, it does not replace', doc '{ "foo": [ 1, 2, 3 ] }' patch '[ { "op": "copy", "from": "\/foo\/0", "path": "\/foo\/1" } ]' : OK
 Testing 'null value should be valid array element to be removed', doc '{ "foo": [ null, 1 ] }' patch '[ { "op": "remove", "path": "\/foo\/0" } ]' : OK
 Testing 'test should pass despite rearrangement', doc '{ "foo": { "foo": 1, "bar": 2 } }' patch '[ { "op": "test", "path": "\/foo", "value": { "bar": 2, "foo": 1 } } ]' : OK
 Testing 'test should pass despite (nested) rearrangement', doc '{ "foo": [ { "foo": 1, "bar": 2 } ] }' patch '[ { "op": "test", "path": "\/foo", "value": [ { "bar": 2, "foo": 1 } ] } ]' : OK