feat: add helm env var config exporter

lib/postal/helm_config_exporter.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+require "konfig/exporters/abstract"
+
+module Postal
+  class HelmConfigExporter < Konfig::Exporters::Abstract
+
+    def export
+      contents = []
+
+      path = []
+
+      @schema.groups.each do |group_name, group|
+        path << group_name
+        group.attributes.each do |name, attr|
+          env_var = Konfig::Sources::Environment.path_to_env_var(path + [name])
+          contents << <<~VAR.strip
+            {{ include "app.envVar" (dict "name" "#{env_var}" "spec" .Values.postal.#{path.join('.')}.#{name} "root" . ) }}
+          VAR
+        end
+        path.pop
+      end
+
+      contents.join("\n")
+    end
+
+  end
+end