Allow configuring rule syntax with Kubernetes Ingress annotation

docs/content/migration/v2-to-v3-details.md

@@ -541,6 +541,19 @@ it is now unsupported and would prevent Traefik to start.
 
 All Pilot related configuration should be removed from the static configuration.
 
+### Kubernetes Ingress Path Matching
+
+In v3, the Kubernetes Ingress default path matching does not support regexes anymore.
+
+#### Remediation
+
+Two levels of remediation are possible:
+
+- Interpret the default path matcher `PathPrefix` with v2 syntax.
+This can done globally for all routers with the [static configuration](#configure-the-default-syntax-in-static-configuration) or on a per-router basis by using the [traefik.ingress.kubernetes.io/router.rulesyntax](../routing/providers/kubernetes-ingress.md#annotations) annotation.
+
+- Adapt the path regex to be compatible with the Go regex syntax and change the default path matcher to use the `PathRegexp` matcher with the [`traefik.ingress.kubernetes.io/router.pathmatcher`](../routing/providers/kubernetes-ingress.md#annotations) annotation.
+
 ## Operations Changes
 
 ### Traefik RBAC Update

docs/content/routing/providers/kubernetes-ingress.md

@@ -229,10 +229,18 @@ which in turn will create the resulting routers, services, handlers, etc.
     traefik.ingress.kubernetes.io/router.priority: "42"
     ```
 
+??? info "`traefik.ingress.kubernetes.io/router.rulesyntax`"
+
+    See [rule syntax](../routers/index.md#rulesyntax) for more information.
+
+    ```yaml
+    traefik.ingress.kubernetes.io/router.rulesyntax: "v2"
+    ```
+
 ??? info "`traefik.ingress.kubernetes.io/router.pathmatcher`"
 
     Overrides the default router rule type used for a path.
-    Only path-related matcher name can be specified: `Path`, `PathPrefix`.
+    Only path-related matcher name should be specified: `Path`, `PathPrefix` or `PathRegexp`.
 
     Default `PathPrefix`