Preserve GRPCRoute filters order

pkg/provider/kubernetes/gateway/fixtures/grpcroute/filter_extension_ref.yml

@@ -0,0 +1,56 @@
+---
+kind: GatewayClass
+apiVersion: gateway.networking.k8s.io/v1
+metadata:
+  name: my-gateway-class
+spec:
+  controllerName: traefik.io/gateway-controller
+
+---
+kind: Gateway
+apiVersion: gateway.networking.k8s.io/v1
+metadata:
+  name: my-gateway
+  namespace: default
+spec:
+  gatewayClassName: my-gateway-class
+  listeners: # Use GatewayClass defaults for listener definition.
+    - name: http
+      protocol: HTTP
+      port: 80
+      allowedRoutes:
+        kinds:
+          - kind: GRPCRoute
+            group: gateway.networking.k8s.io
+        namespaces:
+          from: Same
+
+---
+kind: GRPCRoute
+apiVersion: gateway.networking.k8s.io/v1
+metadata:
+  name: grpc-app-1
+  namespace: default
+spec:
+  parentRefs:
+    - name: my-gateway
+      kind: Gateway
+      group: gateway.networking.k8s.io
+  hostnames:
+    - foo.com
+  rules:
+    - backendRefs:
+        - name: whoami
+          port: 80
+          weight: 1
+      filters:
+        - type: ExtensionRef
+          extensionRef:
+            group: traefik.io
+            kind: Middleware
+            name: my-first-middleware
+        - type: ExtensionRef
+          extensionRef:
+            group: traefik.io
+            kind: Middleware
+            name: my-second-middleware