add payment and integration with midtrans

prisma/schema.prisma

@@ -262,8 +262,11 @@ model Booking {
   createdAt DateTime @default(now())
   updatedAt DateTime @updatedAt
 
+  /// Konsistensi: 1-1 ke participant via participantId, dan participant unique
+  /// per (tripId, userId). Constraint ini eksplisit + jadi index untuk query
+  /// `findByTripAndUser`.
+  @@unique([tripId, userId])
   @@index([tripId, status])
-  @@index([userId])
 }
 
 enum BookingStatus {