code: func updateImageIDs(env map[string]string) bool {
  	updated := false
  	for prefix, newID := range map[string]string{
  		"REDIS":       redisImage.ID,
  		"SLUGBUILDER": slugBuilder.ID,
  		"SLUGRUNNER":  slugRunner.ID,
  	} {
  		idKey := prefix + "_IMAGE_ID"
  		if id, ok := env[idKey]; ok && id != newID {
  			env[idKey] = newID
  			updated = true
  		}
  
  		uriKey := prefix + "_IMAGE_URI"
  		if _, ok := env[uriKey]; ok {
  			delete(env, uriKey)
  			env[idKey] = newID
  			updated = true
  		}
  	}
  	return updated
  }
docs: // updateImageIDs updates REDIS_IMAGE_ID, SLUGBUILDER_IMAGE_ID and
  // SLUGRUNNER_IMAGE_ID if they are set and have an old ID, and also
  // replaces the legacy REDIS_IMAGE_URI, SLUGBUILDER_IMAGE_URI and
  // SLUGRUNNER_IMAGE_URI