🐛 Fix: Infinite Recursion in Form Mapping with Self-Referencing Pointers

Problem

Stack overflow crash occurs when binding query parameters to structs containing self-referencing pointers (e.g., Parent *Req) when no query values are provided.

Root Cause

The mapping function in /binding/form_mapping.go:96 would infinitely create new instances when processing self-referencing struct pointers without termination conditions.

Solution

Implemented a depth limiting mechanism to prevent infinite recursion:

• Added maxMappingDepth = 10 constant for recursion depth control
• Created mappingWithDepth function with depth parameter tracking
• Enhanced pointer processing to validate depth before instance creation
• Maintains 100% backward compatibility with existing API

Files Changed

• binding/form_mapping.go: Added depth limiting logic
• binding/form_mapping_test.go: Added comprehensive test coverage

Test Results

• 3 new test cases pass (including original reported example)
• All 119 existing test cases continue to pass
• Stack overflow issue completely resolved

Fixes #3791