Reject JSON Patch move when from is a proper prefix of path

RFC 6902 (section 4.4) forbids "from" from being a proper prefix of
"path" for a "move" operation: "a location cannot be moved into one
of its children." "move" is implemented as remove-then-add with no
check for this. For object targets, the subsequent "add" happened to
throw as a side effect of resolving through the now-removed parent,
but for array targets, removing the "from" element shifts subsequent
indices, so "path" silently re-resolves to a different element and
the operation "succeeds" with a silently corrupted document.

Add a check, before performing the remove/add, for whether "from" is
a proper prefix of "path" at the reference-token level. This compares
json_pointer's already-unescaped reference_tokens vectors (basic_json
is a friend of json_pointer) rather than the raw pointer strings, so
that tokens containing escaped '/' or '~' characters are compared
correctly, and a token that merely looks like a string prefix (e.g.
"/ab" vs "/abc/x") is not mistaken for a pointer-token prefix. When
"from" is a proper prefix of "path", throw out_of_range.414.

Fixes #5397.

Stacked on top of the fix for #5396 (branch
issue-5396-patch-remove-primitive-parent), since both touch the same
patch_inplace move/remove handling in include/nlohmann/json.hpp.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

docs/mkdocs/docs/api/basic_json/patch.md

@@ -36,6 +36,8 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
   location has a parent that is neither an object nor an array.
 - Throws [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) if a "remove" operation's target
   location has a parent that is neither an object nor an array.
+- Throws [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) if a "move" operation's "from"
+  location is a proper prefix of its "path" location.
 - Throws [`other_error.501`](../../home/exceptions.md#jsonexceptionother_error501) if "test" operation was
   unsuccessful.
 
@@ -79,3 +81,5 @@ is thrown. In any case, the original value is not changed: the patch is applied
   target location has a non-object/non-array parent in version 3.13.0.
 - Added [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) and stopped silently ignoring a "remove" operation whose target
   location has a non-object/non-array parent in version 3.13.0.
+- Added [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) and rejected a "move" operation whose "from" location is a proper
+  prefix of its "path" location instead of silently producing a corrupted result in version 3.13.0.

docs/mkdocs/docs/api/basic_json/patch_inplace.md

@@ -32,6 +32,8 @@ No guarantees, value may be corrupted by an unsuccessful patch operation.
   location has a parent that is neither an object nor an array.
 - Throws [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) if a "remove" operation's target
   location has a parent that is neither an object nor an array.
+- Throws [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) if a "move" operation's "from"
+  location is a proper prefix of its "path" location.
 - Throws [`other_error.501`](../../home/exceptions.md#jsonexceptionother_error501) if "test" operation was
   unsuccessful.
 
@@ -76,3 +78,5 @@ function throws an exception.
   target location has a non-object/non-array parent in version 3.13.0.
 - Added [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) and stopped silently ignoring a "remove" operation whose target
   location has a non-object/non-array parent in version 3.13.0.
+- Added [`out_of_range.414`](../../home/exceptions.md#jsonexceptionout_of_range414) and rejected a "move" operation whose "from" location is a proper
+  prefix of its "path" location instead of silently producing a corrupted result in version 3.13.0.

docs/mkdocs/docs/home/exceptions.md

@@ -947,6 +947,20 @@ A JSON Patch `remove` operation cannot be applied because the target location's
 
     This exception was added in version 3.13.0. Before that, this situation was silently ignored (the `remove` operation had no effect).
 
+### json.exception.out_of_range.414
+
+A JSON Patch `move` operation's `"from"` location is a proper prefix of its `"path"` location. Per [RFC 6902](https://datatracker.ietf.org/doc/html/rfc6902) (section 4.4), a location cannot be moved into one of its own children.
+
+!!! failure "Example message"
+
+    ```
+    cannot move value: 'from' path '/0' is a proper prefix of 'path' '/0/0'
+    ```
+
+!!! note
+
+    This exception was added in version 3.13.0. Before that, this situation could succeed with a corrupted result: for an array target, removing the "from" element before the "add" step shifted subsequent indices, so "path" silently re-resolved to a different element than intended.
+
 ## Further exceptions
 
 This exception is thrown in case of errors that cannot be classified with the