Template action with ID 'slack:sendMessage:webhook' is not registered

[chauvm]

I got this error Template action with ID 'slack:sendMessage:webhook' is not registered when I created an action from a template similar to your example.

# my template
apiVersion: scaffolder.backstage.io/v1beta3
kind: Template
metadata:
  name: slack-message-demo
  title: My Slack message demo
  description: Send a message via Slack
spec:
  owner: someowner
  type: service

  steps:
    # this step is an example of using the webhook action
    - id: send-slack-message
      name: Send slack message via Slack webhook
      action: slack:sendMessage:webhook
      input:
        message: "Hello!"

Here's what I have in apps/backstage/packages/backend/src/index.ts:

import sendSlackMessageModule from '@mdude2314/backstage-plugin-scaffolder-backend-module-slack';
...
backend.add(sendSlackMessageModule());

I noticed there's no slack actions under installed actions via <my-backstage-url>/create/actions. Am I missing some steps to register this action?

[chauvm]

never mind, my container wasn't built properly. This set up works.