text: Title: Add support for querying from partial models
  Body: ## Problem
  
  <!-- A clear and concise description of what the problem is. Ex. I'm always frustrated when [...] -->
  
  Currently partial models cannot be used with model-based access.
  
  ```py
  from prisma.partials import UserOnlyId
  
  user = await UserOnlyId.prisma().find_first(
      where={
          'name': 'Robert',
      },
  )
  ```
  
  ## Suggested solution
  
  <!-- A clear and concise description of what you want to happen. -->
  
  After #19 is implemented, all it would take is adding the `prisma()` classmethod to generated partial types.