json parser: add a configurable maximum nesting depth to the JSON parser #669

What

The JSON library currently accepts documents of arbitrary nesting depth.

Add a bounded nesting depth to the parser, with a sane default and the ability to configure it, so that documents exceeding the limit are rejected with a regular parse error instead of being accepted.

If not implemented there is a risk of stack exhaustion from untrusted input. Parsing itself is iterative, but traversal, comparison, cloning, serialization and destruction of the resulting tree are recursive. A deeply nested document is accepted at parse time and then crashes the process later, in unrelated code.

Acceptance Criteria (DoD)

• The parser rejects documents whose nesting depth exceeds the configured limit, returning a normal parse error.
• A default limit is defined and documented.
• The limit is configurable by the integrator.

How

No response