Upgrade to Prisma-2.0.0-beta.4

[thedavidprice]

Prisma release notes: https://github.com/prisma/prisma/releases/tag/2.0.0-beta.4

• Support for JSON types unknown if JSON will work with RW, but experiment in progress here https://community.redwoodjs.com/t/jsonb-support-from-prisma-2-0-0-beta4/508/5
• Support for Yarn workspaces I'm not sure this applies to RW's setup. In any event, a simple test running yarn prisma generate from root failed. This likely has more to do with installation than CLI.
• Prisma Studio tests running yarn prisma studio --experimental failed. It does not seem studio supports the use of env(...) in the schema. Nor supports workspaces (running from api/ couldn't find client in root 'node_modules/.prisma/'

Passing manual tests locally:

• yarn rw db save
• yarn rw db up
• yarn rw dev
• DB migration file compatibility from beta.3 to beta.4
• CRUD query/mutations for tutorial blog posts
  ⚠️ I have not yet tested deploy. To do before a new release.