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>

pkg/apis/acid.zalan.do/v1/crds.go

@@ -942,6 +942,9 @@ var OperatorConfigCRDResourceValidation = apiextv1beta1.CustomResourceValidation
 							"pod_environment_configmap": {
 								Type: "string",
 							},
+							"pod_environment_secret": {
+								Type: "string",
+							},
 							"pod_management_policy": {
 								Type: "string",
 								Enum: []apiextv1beta1.JSON{

pkg/apis/acid.zalan.do/v1/operator_configuration_type.go

@@ -70,6 +70,7 @@ type KubernetesMetaConfiguration struct {
 	// TODO: use a proper toleration structure?
 	PodToleration              map[string]string   `json:"toleration,omitempty"`
 	PodEnvironmentConfigMap    spec.NamespacedName `json:"pod_environment_configmap,omitempty"`
+	PodEnvironmentSecret       string              `json:"pod_environment_secret,omitempty"`
 	PodPriorityClassName       string              `json:"pod_priority_class_name,omitempty"`
 	MasterPodMoveTimeout       Duration            `json:"master_pod_move_timeout,omitempty"`
 	EnablePodAntiAffinity      bool                `json:"enable_pod_antiaffinity,omitempty"`