Implement 'endpoint' attribute of request object

[olexandr-klymenko]

In my use case I need to have the endpoint attribute in request object which should contain name of coro (1-st argument of endpoint coro) similarly to Flask request.endpoint, i.e.:

@app.middleware('response')
def _after_request(request, response):

    def make_request_id():
        return '.'.join([request.endpoint, request.method.lower(), str(uuid4())])

    request_id = make_request_id()
    response.headers[REQUEST_ID_HEADER] = request_id
    return response

endpoint can be automatically created with blueprint decorator:

@blueprint.get("", strict_slashes=True)
async def get_profile(request):
    return response.json({
        'user_id': '0',
        'profile_id': 0,
        'nickname': 'Nickname'
    }, 200)

i.e. in this case request.endpoint is 'get_profile'

[ahopkins]

Done.