Create Traefik middlewares in nextjs chart

charts/nextjs/templates/ingress-external.yaml

@@ -11,13 +11,30 @@
     {{- $hasAnyHostWithTls = true }}
   {{- end }}
 {{- end -}}
+{{- /*
+If .Values.traefikMiddlewares is nonempty, we add a new item to .Values.ingressExternal.annotations:
+The key of this extra item is "traefik.ingress.kubernetes.io/router.middlewares".
+The value is a comma-separated list of items of the form "<namespace>-<x>@kubernetescrd", where <namespace> is the release namespace and <x> is an item in .Values.traefikMiddlewares.
+To the best of my knowledge, we need to construct this string in this template instead of letting users specify a Traefik middleware annotation themselves in ingressExternal.annotations because the names must contain the namespace, which is not available in the values.yaml file (or wherever the user overrides the values).
+*/}}
+{{- $additionalAnnotations := dict }}
+{{- if .Values.traefikMiddlewares }}
+  {{- $namespace := .Release.Namespace }}
+  {{- $middlewares := list }}
+  {{- range $name, $spec := .Values.traefikMiddlewares }}
+    {{- $middleware := printf "%s-%s@kubernetescrd" $namespace $name }}
+    {{- $middlewares = append $middlewares $middleware }}
+  {{- end }}
+  {{- $additionalAnnotations = dict "traefik.ingress.kubernetes.io/router.middlewares" (join "," $middlewares) }}
+{{- end }}
+{{- $mergedAnnotations := merge .Values.ingressExternal.annotations $additionalAnnotations }}
 apiVersion: networking.k8s.io/v1
 kind: Ingress
 metadata:
   name: {{ $fullName }}-external
   labels:
     {{- include "nextjs-helm.labels" . | nindent 4 }}
-  {{- with .Values.ingressExternal.annotations }}
+  {{- with $mergedAnnotations }}
   annotations:
     {{- toYaml . | nindent 4 }}
   {{- end }}

charts/nextjs/templates/middlewares.yaml

@@ -0,0 +1,9 @@
+{{- range $name, $spec := .Values.traefikMiddlewares }}
+---
+apiVersion: traefik.io/v1alpha1
+kind: Middleware
+metadata:
+  name: {{ $name }}
+spec:
+  {{- $spec | toYaml | nindent 2 }}
+{{- end }}

charts/nextjs/values.yaml

@@ -99,6 +99,13 @@ externalHosts: []
 #    tls: true
 #    path: /
 
+# If `traefikMiddlewares` is nonempty, middleware resources are created and a `traefik.ingress.kubernetes.io/router.middlewares` annotation is added to the ones already in `ingressExternal.annotations`
+traefikMiddlewares: {}
+  # example-redirect:
+  #   redirectRegex:
+  #     regex: ^https://example\.com/$
+  #     replacement: https://example\.org/
+
 resources: {}
   # We usually recommend not to specify default resources and to leave this as a conscious
   # choice for the user. This also increases chances charts run on environments with little