Refactor onboarding user vars to be absent when user is fully onboarded (#6531)

In this PR:
- take feedbacks from: https://github.com/twentyhq/twenty/pull/6530 /
https://github.com/twentyhq/twenty/pull/6529 /
https://github.com/twentyhq/twenty/pull/6526 /
https://github.com/twentyhq/twenty/pull/6512
- refactor onboarding uservars to be absent when the user is fully
onboarded: isStepComplete ==> isStepIncomplete
- introduce a new workspace.activationStatus: CREATION_ONGOING

I'm retesting the whole flow:
- with/without BILLING
- sign in with/without SSO
- sign up with/without SSO
- another workspaceMembers join the team
- subscriptionCanceled
- access to billingPortal

packages/twenty-server/src/modules/workflow/common/workflow-common.module.ts

@@ -1,4 +1,4 @@
-import { Global, Module } from '@nestjs/common';
+import { Module } from '@nestjs/common';
 
 import { WorkflowCommonService } from 'src/modules/workflow/common/workflow-common.services';