Added support for middleware as: func(request, next)

[protibimbok]

Add support for per route middleware

Route Middlewares

The route middlewares behaves more like an endpoint than a middleware.
These middlewares receive two parameters request: Request and next: async function

async def check_admin(request: Request, next):
    if request.headers['Authorization'] == 'I am admin':
        request.isAdmin = True
        request.perms = ['a', 'b', 'c']
        return await next()
    else:
        return JSONResponse({'error':'Unauthorized access'})


async def check_perm(request: Request, next):
    if request.isAdmin and 'c' in request.perms:
        response = await next() # you can now do stuff with the response
        if type(response) == str:
            response = Response(response, media_type="text/plain")
        elif type(response) == dict:
            response = JSONResponse(response)

        return response
    else:
        return JSONResponse({'error':'Unauthorized access'})



routes = [
    Route("/admin", endpoint = admin_page, middlewares = check_admin),
    Route(
        "/admin/secret", endpoint = admin_secret,
        middlewares = [check_admin, check_perm] # Middlewares will be ran in the same order
    )
]

[Kludex]

Thanks for the PR!

• This was discussed on feat: Add route-level middleware #1286, then the idea was reworked on feat: add middleware to Router #1464, and finally the idea was rereworked on Add Mount(..., middleware=[...]) #1649.

Also, this PR is more complex, and breaks how we propose to structure Starlette: blocks of ASGI applications.

For that reason, I'll be closing this PR.