message: activate workflow epilogue
diff: @@ -7,6 +7,7 @@ import { WorkflowPostable } from '@cardstack/web-client/models/workflow/workflow
  import { Workflow } from '@cardstack/web-client/models/workflow';
  import { Milestone } from '@cardstack/web-client/models/workflow/milestone';
  import { WorkflowCard } from '@cardstack/web-client/models/workflow/workflow-card';
  +import PostableCollection from '@cardstack/web-client/models/workflow/postable-collection';
  let cardbot = { name: 'Cardbot', imgURL: '/images/icons/cardbot.svg' };
  @@ -144,7 +145,7 @@ class DepositWorkflow extends Workflow {
  completedDetail: 'Tokens received on xDai',
  }),
  ];
  - epiloguePostables = [
  + epilogue = new PostableCollection([
  new WorkflowMessage({
  author: cardbot,
  message: 'Thank you for your contribution!',
  @@ -174,7 +175,7 @@ class DepositWorkflow extends Workflow {
  author: cardbot,
  componentName: 'card-pay/deposit-workflow/next-steps',
  }),
  - ];
  + ]);
  constructor(owner: unknown) {
  super(owner);
  this.attachWorkflow();
  