Add support for middleware

[RobertCraigie]

https://www.prisma.io/docs/concepts/components/prisma-client/middleware

client = Client()

async def logging_middleware(params: MiddlewareParams, next: NextMiddleware) -> MiddlewareResult:
    log.info('Running %s query on %s', params.action, params.model)
    yield await next(params)
    log.info('Successfully ran %s query on %s ', params.action, params.model)

async def foo_middleware(params: MiddlewareParams, next: NextMiddleware) -> MiddlewareResult:
    ...
    result = await next(params)
    ...
    return result

client.use(logging_middleware, foo_middleware)

Should Support

• Yielding result
• Returning result

[RobertCraigie]

We should also provide utility functions for modifying arguments.

This would make correctly implementing a feature like soft deletes easy.

I will make this a separate issue when I've designed an API proposal.