add deploy env users validator

devops-service/db/validators/deploy_env/users.rb

@@ -0,0 +1,14 @@
+module Validators
+  class DeployEnv::Users < Base
+
+    def valid?
+      mongo_users = DevopsService.mongo.users_names(@model.users)
+      @nonexistent_users = @model.users - mongo_users
+      @nonexistent_users.empty?
+    end
+
+    def message
+      "These users are missing in mongo: '#{@nonexistent_users.join("', '")}'."
+    end
+  end
+end