Allow pod environment variables to also be sourced from a secret (#946)

* Extend operator configuration to allow for a pod_environment_secret just like pod_environment_configmap

* Add all keys from PodEnvironmentSecrets as ENV vars (using SecretKeyRef to protect the value)

* Apply envVars from pod_environment_configmap and pod_environment_secrets before doing the global settings from the operator config. This allows them to be overriden by the user (via configmap / secret)

* Add ability use a Secret for custom pod envVars (via pod_environment_secret) to admin documentation

* Add pod_environment_secret to Helm chart values.yaml

* Add unit tests for PodEnvironmentConfigMap and PodEnvironmentSecret - highly inspired by @kupson and his very similar PR #481

* Added new parameter pod_environment_secret to operatorconfig CRD and configmap examples

* Add pod_environment_secret to the operationconfiguration CRD

Co-authored-by: Christian Rohmann <christian.rohmann@inovex.de>

manifests/configmap.yaml

@@ -74,6 +74,7 @@ data:
   # pod_antiaffinity_topology_key: "kubernetes.io/hostname"
   pod_deletion_wait_timeout: 10m
   # pod_environment_configmap: "default/my-custom-config"
+  # pod_environment_secret: "my-custom-secret"
   pod_label_wait_timeout: 10m
   pod_management_policy: "ordered_ready"
   pod_role_label: spilo-role

manifests/operatorconfiguration.crd.yaml

@@ -145,6 +145,8 @@ spec:
                   type: string
                 pod_environment_configmap:
                   type: string
+                pod_environment_secret:
+                  type: string
                 pod_management_policy:
                   type: string
                   enum:

manifests/postgresql-operator-default-configuration.yaml

@@ -49,6 +49,7 @@ configuration:
     pdb_name_format: "postgres-{cluster}-pdb"
     pod_antiaffinity_topology_key: "kubernetes.io/hostname"
     # pod_environment_configmap: "default/my-custom-config"
+    # pod_environment_secret: "my-custom-secret"
     pod_management_policy: "ordered_ready"
     # pod_priority_class_name: ""
     pod_role_label: spilo-role