add fetch billing products from tables instead of env variables (#9601)

Solves https://github.com/twentyhq/private-issues/issues/237

**TLDR:**

- Fetches billing products and prices from the tables BilllingProducts
and BillingPrices instead of fetching the product from the environment
variables and the prices from the stripe API.
- Adds new feature flag for this feature
- Fixes calls used to fetch stripe products and prices for the command
Billing Sync Plans Data.


**In order to test:**

1. Have the environment variable IS_BILLING_ENABLED set to true and add
the other required environment variables for Billing to work
2. Do a database reset (to ensure that the new feature flag is properly
added and that the billing tables are created)
3. Run the command: `npx nx run twenty-server:command
billing:sync-plans-data` (if you don't do that the products and prices
will not be present in the database)
4. Run the server , the frontend, the worker, and the stripe listen
command (`stripe listen --forward-to
http://localhost:3000/billing/webhooks`)
5. Buy a subscription for the Acme workspace and play with the project

**Doing**

I think there is some room of progress for the function
formatProductPrices, I used a similar version that was done before, I'll
look into that.

packages/twenty-server/src/database/typeorm-seeds/core/feature-flags.ts

@@ -50,6 +50,11 @@ export const seedFeatureFlags = async (
         workspaceId: workspaceId,
         value: true,
       },
+      {
+        key: FeatureFlagKey.IsBillingPlansEnabled,
+        workspaceId: workspaceId,
+        value: true,
+      },
       {
         key: FeatureFlagKey.IsGmailSendEmailScopeEnabled,
         workspaceId: workspaceId,

packages/twenty-server/src/database/typeorm/core/migrations/billing/1737127856478-addNonNullableProductDescription.ts

@@ -0,0 +1,25 @@
+import { MigrationInterface, QueryRunner } from 'typeorm';
+
+export class AddNonNullableProductDescription1737127856478
+  implements MigrationInterface
+{
+  name = 'AddNonNullableProductDescription1737127856478';
+
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(
+      `ALTER TABLE "core"."billingProduct" ALTER COLUMN "description" SET DEFAULT ''`,
+    );
+    await queryRunner.query(
+      `ALTER TABLE "core"."billingProduct" ALTER COLUMN "description" SET NOT NULL`,
+    );
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(
+      `ALTER TABLE "core"."billingProduct" ALTER COLUMN "description" DROP DEFAULT`,
+    );
+    await queryRunner.query(
+      `ALTER TABLE "core"."billingProduct" ALTER COLUMN "description" DROP NOT NULL`,
+    );
+  }
+}