Add Paddle checkout foundation

backend/prisma/migrations/20260708130000_milestone121_checkout_customer_foundation_correction/migration.sql

@@ -0,0 +1,45 @@
+CREATE TABLE "billing_customers" (
+  "id" UUID NOT NULL,
+  "user_id" UUID NOT NULL,
+  "provider" "BillingProvider" NOT NULL,
+  "provider_customer_id" TEXT NOT NULL,
+  "created_at" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  "updated_at" TIMESTAMP(3) NOT NULL,
+  CONSTRAINT "billing_customers_pkey" PRIMARY KEY ("id")
+);
+
+CREATE UNIQUE INDEX "billing_customers_user_id_key"
+ON "billing_customers"("user_id");
+
+CREATE UNIQUE INDEX "billing_customers_provider_customer_id_key"
+ON "billing_customers"("provider_customer_id");
+
+ALTER TABLE "billing_customers"
+ADD CONSTRAINT "billing_customers_user_id_fkey"
+FOREIGN KEY ("user_id") REFERENCES "users"("id")
+ON DELETE CASCADE
+ON UPDATE CASCADE;
+
+INSERT INTO "billing_customers" (
+  "id",
+  "user_id",
+  "provider",
+  "provider_customer_id",
+  "created_at",
+  "updated_at"
+)
+SELECT
+  gen_random_uuid(),
+  "user_id",
+  "provider",
+  "provider_customer_id",
+  NOW(),
+  NOW()
+FROM "user_subscriptions"
+WHERE "provider_customer_id" IS NOT NULL
+ON CONFLICT ("user_id") DO NOTHING;
+
+DROP INDEX "user_subscriptions_provider_customer_id_key";
+
+ALTER TABLE "user_subscriptions"
+DROP COLUMN "provider_customer_id";

backend/prisma/schema.prisma

@@ -34,6 +34,7 @@ model User {
   incomingTransfers       OwnershipTransfer[]      @relation("OwnershipTransferToUser")
   initiatedTransfers      OwnershipTransfer[]      @relation("OwnershipTransferRequestedByUser")
   accountSessions         AccountSession[]
+  billingCustomer         BillingCustomer?
   subscription            UserSubscription?
   entitlements            UserEntitlement[]
 
@@ -304,11 +305,22 @@ model AccountSession {
   @@map("account_sessions")
 }
 
+model BillingCustomer {
+  id                 String          @id @default(uuid()) @db.Uuid
+  userId             String          @unique @map("user_id") @db.Uuid
+  provider           BillingProvider
+  providerCustomerId String          @unique @map("provider_customer_id")
+  createdAt          DateTime        @default(now()) @map("created_at")
+  updatedAt          DateTime        @updatedAt @map("updated_at")
+  user               User            @relation(fields: [userId], references: [id], onDelete: Cascade, onUpdate: Cascade)
+
+  @@map("billing_customers")
+}
+
 model UserSubscription {
   id                     String             @id @default(uuid()) @db.Uuid
   userId                 String             @unique @map("user_id") @db.Uuid
   provider               BillingProvider
-  providerCustomerId     String?            @unique @map("provider_customer_id")
   providerSubscriptionId String?            @unique @map("provider_subscription_id")
   plan                   SubscriptionPlan
   status                 SubscriptionStatus