fix: Allow less than 30 seats for orgs (#14995)

* fix: Allow less than 30 seats for orgs

* Add test

* Stub env variables

apps/api/v1/pages/api/teams/[teamId]/_patch.ts

@@ -107,7 +107,7 @@ export async function patchHandler(req: NextApiRequest) {
     if (IS_TEAM_BILLING_ENABLED) {
       const checkoutSession = await purchaseTeamOrOrgSubscription({
         teamId: _team.id,
-        seats: _team.members.length,
+        seatsUsed: _team.members.length,
         userId,
         pricePerSeat: null,
       });