decorators support

[ruckc]

It would be nice if this style was supported to make it more sanic like. Essentially use decorators to add the checks, just like decorators add routes to the app.

app=Sanic("app")
hc = HealthCheck(app)


@app.get("/")
async def index(request):
    return text("Hello world")

@hc.check()
async def check_db():
    result = await db.ping()
    return True, "connected" if result else False, "disconnected"