code: func validateProjectConfig(ctx *validation.Context, projectCfg *notifypb.ProjectConfig) {
  	builderNames := stringset.New(len(projectCfg.Notifiers)) // At least one builder per notifier
  	for i, cfgNotifier := range projectCfg.Notifiers {
  		ctx.Enter("notifier #%d", i+1)
  		validateNotifier(ctx, cfgNotifier, builderNames)
  		ctx.Exit()
  	}
  }
docs: // validateProjectConfig returns an error if the configuration violates any of the
  // requirements in the proto definition.