[explorer] Allow specifying extra ingress rules

This can be used to, for example with the AWS ALB Ingress Controller:
- create redirects to a canonical hostname
- create static responses containing a small robots.txt

stable/datacube-explorer/templates/ingress.yaml

@@ -33,5 +33,7 @@ spec:
                 port:
                   number: {{ $externalPort }}
     {{- end }}
-
+{{- with .Values.ingress.extraRules}}
+{{ toYaml . | indent 4}}
+{{- end }}
 {{- end }}

stable/datacube-explorer/values.yaml

@@ -88,3 +88,10 @@ ingress:
   hosts:
     - ""
   annotations: {}
+#  extraRules:
+#    - host: hello.world
+#      paths:
+#        - path: "/robots.txt"
+#          backend:
+#            service:
+#              name: what