IngressRoute: add an option to disable cross-namespace routing

Co-authored-by: Jean-Baptiste Doumenjou <925513+jbdoumenjou@users.noreply.github.com>

integration/fixtures/k8s/07-ingressroute-cross-namespace.yml

@@ -0,0 +1,120 @@
+---
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: other-ns
+
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: whoami
+  namespace: other-ns
+
+spec:
+  ports:
+    - name: http
+      port: 80
+  selector:
+    app: traefiklabs
+    task: whoami
+
+---
+apiVersion: traefik.containo.us/v1alpha1
+kind: IngressRoute
+metadata:
+  name: test6.route
+  namespace: other-ns
+
+spec:
+  entryPoints:
+    - web
+  routes:
+  - match: Host(`foo.com`) && PathPrefix(`/a`)
+    kind: Rule
+    services:
+    - name: whoami
+      namespace: default
+      port: 80
+  - match: Host(`foo.com`) && PathPrefix(`/b`)
+    kind: Rule
+    services:
+    - name: wrr2
+      namespace: default
+      kind: TraefikService
+  - match: Host(`foo.com`) && PathPrefix(`/c`)
+    kind: Rule
+    services:
+    - name: wrr3
+      kind: TraefikService
+  - match: Host(`foo.com`) && PathPrefix(`/d`)
+    kind: Rule
+    services:
+    - name: whoami
+      namespace: other-ns
+      port: 80
+    middlewares:
+    - name: stripprefix2
+      namespace: default
+  - match: Host(`foo.com`) && PathPrefix(`/e`)
+    kind: Rule
+    services:
+    - name: whoami
+      port: 80
+    middlewares:
+    - name: test-errorpage
+
+---
+apiVersion: traefik.containo.us/v1alpha1
+kind: TraefikService
+metadata:
+  name: wrr2
+  namespace: default
+
+spec:
+  weighted:
+    services:
+      - name: whoami
+        port: 80
+
+---
+apiVersion: traefik.containo.us/v1alpha1
+kind: TraefikService
+metadata:
+  name: wrr3
+  namespace: other-ns
+
+spec:
+  weighted:
+    services:
+      - name: whoami
+        namespace: default
+        port: 80
+
+---
+apiVersion: traefik.containo.us/v1alpha1
+kind: Middleware
+metadata:
+  name: stripprefix2
+  namespace: default
+
+spec:
+  stripPrefix:
+    prefixes:
+      - /tobestripped
+
+---
+apiVersion: traefik.containo.us/v1alpha1
+kind: Middleware
+metadata:
+  name: test-errorpage
+
+spec:
+  errors:
+    status:
+      - 500-599
+    query: /{status}.html
+    service:
+      name: whoami
+      namespace: other-ns
+      port: 80

integration/fixtures/k8s_crd.toml

@@ -16,3 +16,4 @@
     address = ":8000"
 
 [providers.kubernetesCRD]
+  allowCrossNamespace = false