Add Auth.Clear() method and enhance middlewares to clear invalid cookiesHEADmain

- Add Auth.Clear() method that creates expired cookies (MaxAge: -1) to log out users
- Enhance Clear() to remove existing Set-Cookie headers to comply with RFC 6265
- Update Required() and Optional() middlewares to automatically clear invalid cookies
- Add comprehensive tests for all new functionality
- Update documentation with Auth.Clear() usage examples

1 files changed, 3 insertions, 0 deletions

diff --git a/doc.go b/doc.go
index 8d60f2a..12c314d 100644
--- a/doc.go
+++ b/doc.go
@@ -39,6 +39,9 @@
 //	user := UserData{ID: 123, Name: "John"}
 //	auth.Set(w, user)
 //
+//	// Clear authentication cookie (logout)
+//	auth.Clear(w)
+//
 //	// Get authenticated data
 //	user, ok := auth.Get(r.Context())
 //