Alert Google login error details

[sherryhli]

Ticket link

N/A, just a quick fix to display Google login error details properly.

Implementation description

• Correctly typed the Google login error response for future reference
• Stringified error object in alert message, otherwise it will display as [Object object]

Steps to test

1. Click on the preview deploy link below
2. Error message should be as follows:

{
    "error": "idpiframe_initialization_failed",
    "details":"Not a valid origin for the client: https://sistering-dev--pr78-sherry-google-login-ulm92vdz.web.app has not been registered for client ID 1076597678761-u9ek25jknj77d37atud522vb4ri1385t.apps.googleusercontent.com. Please go to https://console.developers.google.com/ and register this origin for your project's client ID."
}

Note that this error is expected because the preview URL is not listed as an authorized origin for our OAuth client. It does not come up in the staging environment.

What should reviewers focus on?

• Nothing in particular, does it work?

Checklist

• My PR name is descriptive and in imperative tense
• My commit messages are descriptive and in imperative tense. My commits are atomic and trivial commits are squashed or fixup'd into non-trivial commits
• I have run the appropriate linter(s)
• I have requested a review from the PL, as well as other devs who have background knowledge on this PR or who will be building on top of this PR

[github-actions]

Visit the preview URL for this PR (updated for commit 4361c51):

https://sistering-dev--pr78-sherry-google-login-ulm92vdz.web.app

_{(expires Sat, 29 Jan 2022 04:20:10 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

[LenaNguyen]