Social Signup: Handle the case where users block third-party cookies/data

[fabianapsimoes]

Reported by @aerych:

We need to handle the case where users block third-party cookies/data. We should message to the user that they need to allow these if they want to connect their social account, instead of just silently failing.

[fabianapsimoes]

@ranh we would need copy for this as well.

[kristastevens]

Standing by @ranh, if you'd an extra set of eyes on the copy.

[ranh]

From @aerych's report, when the Chrome option "Block third-party cookies and site data" is enabled, the "Continue with Google" button becomes unresponsive and returns a console error when clicked.

What about something like this?

Your privacy settings are blocking us from connecting to your Google account. Please enable "third-party cookies" in your browser or operating system, or log in with an email address instead.

We should do a bit more testing with different environments / privacy settings. Depending on the scope of this issue, perhaps we can add a support page with more information and instructions for common browsers and OSs.