…len-parameter

Fixed #657 Param $len should not be implicitly nullable.

- Add maxDepth parameter to Body constructor
- Update Body::serialize() to use maxDepth when calling serializeForRollbar
- Update DataBuilder to pass maxNestingDepth config to Body constructor
- Add test to verify deep nesting is properly truncated

This fixes memory exhaustion issues when logging errors with complex
nested data structures (like Drupal form arrays) by respecting the
configured max_nesting_depth limit during Body serialization.

Previously, Body::serialize() always used unlimited depth (-1) via
serializeForRollbarInternal(), ignoring the max_nesting_depth config.

Fixes memory issues similar to those described in issue reports about
Rollbar consuming excessive memory with deeply nested context data.

Fix: Body serialization should respect max_nesting_depth config

Release v4.1.4