Cookies: Setting the expiration property fails while adding cookies

[inancgumus]

There is a problem while converting the expires property (in seconds) to cdproto's cdp.TimeSinceEpoch.

1. Users provide seconds since Unix time epoch while passing the expires property.
2. CDP and cdproto require setting an exact date (time since epoch).
3. We directly pass the property to cdproto while it expects us a time.Time for setting an expiration date for cookies.

xk6-browser version

v1.0.2

Steps to reproduce the problem

Add a cookie with an expiration property (in seconds).

context.addCookies([{
  name: 'foo',
  value: '42',
  domain: '127.0.0.1',
  path: '/',
  expires: 10,  // <---
}]);

Expected behaviour

Cookies should be added with an expiration date.

Actual behaviour

ERRO[0000] Uncaught (in promise) GoError:
cannot recognize cookie values:
could not convert array element [object Object] to []network.CookieParam at 0:
could not convert struct value 10 to *cdp.TimeSinceEpoch for field Expires:
could not convert 10 to cdp.TimeSinceEpoch

Suggestion

The current addCookies API accepts an internal cookie object: cdproto.network.Cookie. This object contains superfluous information and can be dangerous because it lets users set internal CDP details from their scripts. We can use api.Cookie instead of cdproto.network.Cookie to be consistent with our BrowserContext.cookies API. And also prevent possible security problems.

Updates: #6