fix(router): preserve HTTP method when handling double-slash paths

[Himanshugulhane27]

Description

Fixes #2643

This PR addresses a critical routing bug where HTTP POST requests with double-slash paths (//hello) are incorrectly routed to GET handlers when both methods are registered for the same endpoint.

Problem Statement

Current Behavior:

a.GET("/hello", getHandler)
a.POST("/hello", postHandler)

// Both requests incorrectly hit the GET handler
curl -X POST http://localhost:9000//hello  // ❌ Routes to GET
curl -X GET http://localhost:9000//hello   // ✓ Routes to GET

Impact:

• POST operations are incorrectly processed as GET requests
• Potential security vulnerability (method-based access control bypass)
• Breaks RESTful API semantics
• Violates HTTP specification for method handling

Root Cause

The router initialization uses StrictSlash(false), causing Gorilla Mux to silently normalize paths with double slashes. During this normalization, the HTTP method context is lost, and the router defaults to the first registered handler for the normalized path.

Solution

Enable StrictSlash(true) in router configuration to handle path normalization via HTTP 301 redirects instead of silent normalization. This preserves the HTTP method throughout the redirect flow.

After Fix:

// Both requests now correctly redirect with method preservation
curl -X POST http://localhost:9000//hello  // 301 → POST /hello ✓
curl -X GET http://localhost:9000//hello   // 301 → GET /hello ✓

Changes

File	Change	Lines
pkg/gofr/http/router.go	StrictSlash(false) → StrictSlash(true)	1
pkg/gofr/http/router_test.go	Added TestDoubleSlashRouting	+23

Testing

Unit Tests

• ✅ POST with double-slash returns 301 redirect
• ✅ GET with double-slash returns 301 redirect
• ✅ HTTP method is preserved in redirect
• ✅ Normal paths (/hello) work without redirects

Manual Testing

# Test POST with double slash
curl -v -X POST http://localhost:9000//hello
# Expected: 301 Moved Permanently, Location: /hello

# Test GET with double slash
curl -v http://localhost:9000//hello
# Expected: 301 Moved Permanently, Location: /hello

Backward Compatibility

• ✅ No breaking changes - properly formatted requests work identically
• ⚠️ Behavior change - malformed paths now return 301 instead of silent normalization
• ✅ Standard HTTP behavior - 301 redirects are expected for path normalization
• ✅ Client compatibility - most HTTP clients follow redirects automatically

Checklist

• Code follows project style guidelines
• Added unit tests for the fix
• All existing tests pass
• No breaking changes introduced
• Documentation updated (if needed)
• Commit message follows conventional commits

Additional Notes

This fix aligns with standard HTTP router behavior (similar to Express.js, Gin, etc.) where path normalization is handled via redirects rather than silent rewriting.