feat: add multi subscription support (#734)

## Description

Previously we assumed that there can only be 1 subscription per user.
However, that will soon no longer the case with the introduction of the
Teams subscription.

This PR will apply the required migrations to support multiple
subscriptions.

## Changes Made

- Updated the Prisma schema to allow for multiple `Subscriptions` per
`User`
- Added a Stripe `customerId` field to the `User` model
- Updated relevant billing sections to support multiple subscriptions

## Testing Performed

- Tested running the Prisma migration on a demo database created on the
main branch

Will require a lot of additional testing.

## Checklist

- [ ] I have tested these changes locally and they work as expected.
- [ ] I have added/updated tests that prove the effectiveness of these
changes.
- [X] I have followed the project's coding style guidelines.

## Additional Notes

Added the following custom SQL statement to the migration:

> DELETE FROM "Subscription" WHERE "planId" IS NULL OR "priceId" IS
NULL;

Prior to deployment this will require changes to Stripe products:
- Adding `type` meta attribute

---------

Co-authored-by: Lucas Smith <me@lucasjamessmith.me>

apps/web/src/app/(dashboard)/settings/billing/page.tsx

@@ -2,12 +2,15 @@ import { redirect } from 'next/navigation';
 
 import { match } from 'ts-pattern';
 
+import { getStripeCustomerByUser } from '@documenso/ee/server-only/stripe/get-customer';
 import { getPricesByInterval } from '@documenso/ee/server-only/stripe/get-prices-by-interval';
+import { getPricesByType } from '@documenso/ee/server-only/stripe/get-prices-by-type';
 import { getProductByPriceId } from '@documenso/ee/server-only/stripe/get-product-by-price-id';
 import { getRequiredServerComponentSession } from '@documenso/lib/next-auth/get-server-component-session';
 import { getServerComponentFlag } from '@documenso/lib/server-only/feature-flags/get-server-component-feature-flag';
-import type { Stripe } from '@documenso/lib/server-only/stripe';
-import { getSubscriptionByUserId } from '@documenso/lib/server-only/subscription/get-subscription-by-user-id';
+import { type Stripe } from '@documenso/lib/server-only/stripe';
+import { getSubscriptionsByUserId } from '@documenso/lib/server-only/subscription/get-subscriptions-by-user-id';
+import { SubscriptionStatus } from '@documenso/prisma/client';
 
 import { LocaleDate } from '~/components/formatter/locale-date';
 
@@ -15,7 +18,7 @@ import { BillingPlans } from './billing-plans';
 import { BillingPortalButton } from './billing-portal-button';
 
 export default async function BillingSettingsPage() {
-  const { user } = await getRequiredServerComponentSession();
+  let { user } = await getRequiredServerComponentSession();
 
   const isBillingEnabled = await getServerComponentFlag('app_billing');
 
@@ -24,20 +27,36 @@ export default async function BillingSettingsPage() {
     redirect('/settings/profile');
   }
 
-  const [subscription, prices] = await Promise.all([
-    getSubscriptionByUserId({ userId: user.id }),
-    getPricesByInterval(),
+  if (!user.customerId) {
+    user = await getStripeCustomerByUser(user).then((result) => result.user);
+  }
+
+  const [subscriptions, prices, individualPrices] = await Promise.all([
+    getSubscriptionsByUserId({ userId: user.id }),
+    getPricesByInterval({ type: 'individual' }),
+    getPricesByType('individual'),
   ]);
 
+  const individualPriceIds = individualPrices.map(({ id }) => id);
+
   let subscriptionProduct: Stripe.Product | null = null;
 
+  const individualUserSubscriptions = subscriptions.filter(({ priceId }) =>
+    individualPriceIds.includes(priceId),
+  );
+
+  const subscription =
+    individualUserSubscriptions.find(({ status }) => status === SubscriptionStatus.ACTIVE) ??
+    individualUserSubscriptions[0];
+
   if (subscription?.priceId) {
     subscriptionProduct = await getProductByPriceId({ priceId: subscription.priceId }).catch(
       () => null,
     );
   }
 
-  const isMissingOrInactiveOrFreePlan = !subscription || subscription.status === 'INACTIVE';
+  const isMissingOrInactiveOrFreePlan =
+    !subscription || subscription.status === SubscriptionStatus.INACTIVE;
 
   return (
     <div>