Allow setting shootAdminKubeconfigMaxExpiration in Garden resource. (#519)

Author: Gerrit91

control-plane/roles/gardener-operator/README.md

@@ -67,6 +67,7 @@ Here are the steps for the migration:
 | gardener_operator_virtual_garden_public_dns                   |           | The domain on which the virtual garden istio ingress is exposed                                                                                                                              |
 | gardener_operator_virtual_garden_etcd_storage_class           |           | The storage class used by the virtual garden etcd                                                                                                                                            |
 | gardener_virtual_garden_api_server_version                    |           | The kubernetes version of the virtual garden                                                                                                                                                 |
+| gardener_operator_shoot_admin_kubeconfig_max_expiration       |           | The max expiration for admin kubeconfigs                                                                                                                                                     |
 | gardener_operator_virtual_garden_oidc_issuer_url              |           | [Corresponds to the `--oidc-issuer-url` flag](https://kubernetes.io/docs/reference/access-authn-authz/authentication/#oidc-issuer-url) in the Kubernetes API server configuration.           |
 | gardener_operator_virtual_garden_oidc_client_id               |           | [Corresponds to the `--oidc-client-id` flag](https://kubernetes.io/docs/reference/access-authn-authz/authentication/#oidc-client-id) in the Kubernetes API server configuration.             |
 | gardener_operator_virtual_garden_oidc_username_claim          |           | [Corresponds to the `--oidc-username-claim` flag](https://kubernetes.io/docs/reference/access-authn-authz/authentication/#oidc-username-claim) in the Kubernetes API server configuration.   |

control-plane/roles/gardener-operator/defaults/main/operator.yaml

@@ -37,3 +37,5 @@ gardener_operator_image_vector_overwrite:
 gardener_operator_component_image_vector_overwrite:
 
 gardener_operator_helm_chart_tag: "{{ gardener_operator_image_tag }}"
+
+gardener_operator_shoot_admin_kubeconfig_max_expiration: "24h"

control-plane/roles/gardener-operator/templates/garden.yaml

@@ -188,6 +188,7 @@ spec:
       gardenerAPIServer:
         admissionPlugins:
         - name: ShootVPAEnabledByDefault
+      shootAdminKubeconfigMaxExpiration: "{{ gardener_operator_shoot_admin_kubeconfig_max_expiration }}"
     #   - name: ShootDNSRewriting
     #     disabled: false
     #     config: