Traefik - v2.4.11

Bug fixes:
- [k8s,k8s/crd,k8s/ingress] Disable ExternalName Services by default on Kubernetes providers (#8261 by dtomcej)
- [k8s,k8s/crd,k8s/ingress] Fix: malformed Kubernetes resource names and references in tests (#8226 by rtribotte)
- [k8s,k8s/crd] Disable Cross-Namespace by default for IngressRoute provider (#8260 by dtomcej)
- [logs,middleware] Accesslog: support multiple values for a given header (#8258 by ldez)
- [logs] Ignore http 1.0 request host missing errors (#8252 by dtomcej)
- [middleware] Headers Middleware: support http.CloseNotifier interface (#8238 by dtomcej)
- [tls] Detect certificates content modifications (#8243 by jbdoumenjou)

Documentation:
- [middleware,k8s] Fix invalid subdomain (#8212 by WLun001)
- Add the list of available provider names (#8225 by WLun001)
- Fix maintainers-guidelines page title (#8216 by kubopanda)
- Typos in contributing section (#8215 by kubopanda)