Create database schema using Prisma

Add this following code in your `schema.prisma` file:
```bash
// schema.prisma
datasource db {
provider = "postgresql"
url = env("DATABASE_URL")
}

generator client {
provider = "prisma-client-js"
}

model Post {
id Int @default(autoincrement()) @id
title String
content String?
published Boolean @default(false)
author User? @relation(fields: [authorId], references: [id])
authorId Int?
}

model User {
id Int @default(autoincrement()) @id
name String?
email String? @unique
createdAt DateTime @default(now()) @map(name: "created_at")
updatedAt DateTime @updatedAt @map(name: "updated_at")
posts Post[]
@@map(name: "users")
}
```