Webpage Integration: Social Sign-In

Social sign-in was left out of #2487.
This ticket is created to address it.

By the comments in the PR related to the ticket above, we aren't able to reliably test social sign ins from our local environments, as this would require setting up redirect urls in both providers.
Therefore, in this ticket we must implement the integration, open the PR and coordinate a deployment with QA to test it there, before moving to review.

Start by reviewing issue #2487 and the related pull request comments to understand the omitted social sign-in integration and provider redirect requirements. Implement the integration, open a pull request, coordinate a deployment with QA, and confirm the social sign-ins work there before review.

Written by the indexing model from the issue text.