In chat hooks should not inject the user_id into context manually

[carmenlau]

Now we inject the user id this way in chat sdk.

function chatHook(name, func) {
  skygearCloud.op('chat:' + name + '_hook', function (param, options) {
    const context = {userId: options.context.user_id};
    func(param.args, context);
    return {status: 'ok'};
  }, {
    userRequired: true,
    keyRequired: true
  });
}

That will have 2 problems

1. User will be confusion how to get the user id as it is different from the core lambda
2. After we add more data to the context, new data will be missed in the message hook. For example, we are going to add user verified flag.

Propose solution:
Should configure the container correctly with user for calling the lambda, should not inject the data manually in sdk