environment variable expansion does not support defaults

Bug description

The documentation for Accessing Environment Variables from the Schema explicitly references dotenv-expand for how to do environment variable expansion.

dotenv-expand supports the syntax ${MACHINE:-default}.

See https://github.com/motdotla/dotenv-expand/blob/ed5fea5bf517a09fd743ce2c63150e88c8a5f6d1/tests/.env#L8-L14

variable expansion in prisma does not support this syntax

How to reproduce

1. Make a .env file

# In your .env file
DATABASE_URL=postgresql://${USER}@localhost:5432/myapp_${DATABASE_ENV:-development}

2. Create an initial schema that references the DATABASE_URL in the source
3. run the migration to create the database
4. The database name will be myapp_$%7BDATABASE_ENV:-development%7D

Expected behavior

A new database is created on first migration run with the name of myapp_development

Prisma information

generator client {
  provider = "prisma-client-js"
  previewFeatures = ["interactiveTransactions"]
}

datasource db {
  provider = "postgresql"
  url      = env("DATABASE_URL")
}

model User {
  @@map("users")

// fields
  id String  @id @default(dbgenerated("gen_random_uuid()")) @db.Uuid
  name String?
}

Environment & setup

• OS: Mac OS
• Database: PostgreSQL
• Node.js version: v16.15.1

Prisma Version

Environment variables loaded from .env
Environment variables loaded from db/.env
prisma                  : 3.15.2
@prisma/client          : 3.15.2
Current platform        : darwin-arm64
Query Engine (Node-API) : libquery-engine 461d6a05159055555eb7dfb337c9fb271cbd4d7e (at node_modules/@prisma/engines/libquery_engine-darwin-arm64.dylib.node)
Migration Engine        : migration-engine-cli 461d6a05159055555eb7dfb337c9fb271cbd4d7e (at node_modules/@prisma/engines/migration-engine-darwin-arm64)
Introspection Engine    : introspection-core 461d6a05159055555eb7dfb337c9fb271cbd4d7e (at node_modules/@prisma/engines/introspection-engine-darwin-arm64)
Format Binary           : prisma-fmt 461d6a05159055555eb7dfb337c9fb271cbd4d7e (at node_modules/@prisma/engines/prisma-fmt-darwin-arm64)
Default Engines Hash    : 461d6a05159055555eb7dfb337c9fb271cbd4d7e
Studio                  : 0.462.0
Preview Features        : interactiveTransactions

Start with the .env example and the datasource url env("DATABASE_URL") entry in the schema, then compare its expansion with dotenv-expand's referenced tests/.env syntax. Done means ${DATABASE_ENV:-development} resolves to development when the variable is unset, producing the expected database name during migration.