feat: add teams (#848)

## Description

Add support for teams which will allow users to collaborate on
documents.

Teams features allows users to:

- Create, manage and transfer teams
- Manage team members
- Manage team emails
- Manage a shared team inbox and documents

These changes do NOT include the following, which are planned for a
future release:

- Team templates
- Team API
- Search menu integration

## Testing Performed

- Added E2E tests for general team management
- Added E2E tests to validate document counts

## Checklist

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

packages/lib/server-only/team/leave-team.ts

@@ -0,0 +1,59 @@
+import { updateSubscriptionItemQuantity } from '@documenso/ee/server-only/stripe/update-subscription-item-quantity';
+import { IS_BILLING_ENABLED } from '@documenso/lib/constants/app';
+import { prisma } from '@documenso/prisma';
+
+export type LeaveTeamOptions = {
+  /**
+   * The ID of the user who is leaving the team.
+   */
+  userId: number;
+
+  /**
+   * The ID of the team the user is leaving.
+   */
+  teamId: number;
+};
+
+export const leaveTeam = async ({ userId, teamId }: LeaveTeamOptions) => {
+  await prisma.$transaction(async (tx) => {
+    const team = await tx.team.findFirstOrThrow({
+      where: {
+        id: teamId,
+        ownerUserId: {
+          not: userId,
+        },
+      },
+      include: {
+        subscription: true,
+      },
+    });
+
+    await tx.teamMember.delete({
+      where: {
+        userId_teamId: {
+          userId,
+          teamId,
+        },
+        team: {
+          ownerUserId: {
+            not: userId,
+          },
+        },
+      },
+    });
+
+    if (IS_BILLING_ENABLED && team.subscription) {
+      const numberOfSeats = await tx.teamMember.count({
+        where: {
+          teamId,
+        },
+      });
+
+      await updateSubscriptionItemQuantity({
+        priceId: team.subscription.priceId,
+        subscriptionId: team.subscription.planId,
+        quantity: numberOfSeats,
+      });
+    }
+  });
+};