Billing - Migrate from Stripe metering (#20298)

**Overall strategy**
**1. Introduce “Billing V2” behind a workspace flag**
Gate the new model with FeatureFlagKey.IS_BILLING_V2_ENABLED so existing
workspaces stay on the old behavior until they’re migrated or explicitly
on V2.

**2. Replace workflow metered SKUs with a resource-credit product**
Conceptually, billable “workflow execution” usage is not the primary
subscription line item anymore. Add a RESOURCE_CREDIT product (and keep
WORKFLOW_NODE_EXECUTION as deprecated for the transition). Usage and
limits are expressed through credit buckets (e.g. price metadata like
credit_amount), so one product can represent pooled credits instead of a
narrow workflow-only meter.

**3. Migrate subscriptions in two layers**
Schema/catalog: persist extra price metadata (instance upgrade) so the
server knows credit amounts and can match Stripe prices to the new
model.
Per workspace: the registered workspace command
upgrade:2-2:migrate-to-billing-v2 finds subscriptions that still have
WORKFLOW_NODE_EXECUTION, swaps those items to the right RESOURCE_CREDIT
prices (using existing Stripe schedule +
BillingSubscriptionUpdateService stack), then treats the workspace as V2
(flag). Workspaces without that legacy item or without a subscription
are skipped.

**4. Unify subscription lifecycle + usage on the server**

**5. Refresh the product surface in Settings**

Test : 

- [x] Subscribe v1 +  Update subscribe + Migrate
- [x]  Subscribe v2 + Update subscribe

packages/twenty-front/src/testing/graphqlMocks.ts

@@ -15,6 +15,8 @@ import { mockedPublicWorkspaceDataBySubdomain } from '~/testing/mock-data/public
 import { mockedUserData } from '~/testing/mock-data/users';
 
 import { GET_PUBLIC_WORKSPACE_DATA_BY_DOMAIN } from '@/auth/graphql/queries/getPublicWorkspaceDataByDomain';
+import { BILLING_PORTAL_SESSION } from '@/settings/billing/graphql/queries/billingPortalSession';
+import { GET_METERED_PRODUCTS_USAGE } from '@/settings/billing/graphql/queries/getMeteredProductsUsage';
 import { LIST_PLANS } from '@/settings/billing/graphql/queries/listPlans';
 import { GET_ROLES } from '@/settings/roles/graphql/queries/getRolesQuery';
 import { mockBillingPlans } from '~/testing/mock-data/billing-plans';
@@ -528,6 +530,42 @@ export const graphqlMocks = {
         data: mockBillingPlans,
       });
     }),
+    graphql.query(getOperationName(GET_METERED_PRODUCTS_USAGE) ?? '', () => {
+      return HttpResponse.json({
+        data: {
+          getMeteredProductsUsage: [
+            {
+              __typename: 'BillingMeteredProductUsage',
+              productKey: 'WORKFLOW_NODE_EXECUTION',
+              usedCredits: 1000,
+              grantedCredits: 500000,
+              rolloverCredits: 0,
+              totalGrantedCredits: 500000,
+              unitPriceCents: 1,
+            },
+            {
+              __typename: 'BillingMeteredProductUsage',
+              productKey: 'RESOURCE_CREDIT',
+              usedCredits: 0,
+              grantedCredits: 10000,
+              rolloverCredits: 0,
+              totalGrantedCredits: 10000,
+              unitPriceCents: 1,
+            },
+          ],
+        },
+      });
+    }),
+    graphql.query(getOperationName(BILLING_PORTAL_SESSION) ?? '', () => {
+      return HttpResponse.json({
+        data: {
+          billingPortalSession: {
+            __typename: 'BillingSession',
+            url: 'https://billing.stripe.com/p/mock-portal-session',
+          },
+        },
+      });
+    }),
     http.get('https://chat-assets.frontapp.com/v1/chat.bundle.js', () => {
       return HttpResponse.text(
         `