[Bug] Re-fetch google / github / social provider avatars every login

[matoszz]

Describe the bug or issue you're encountering

If a default avatar or an avatar image is set on initial sign up, and the user changes the avatar, we do not re-fetch the image

What are the relevant steps to reproduce, including the version(s) of the relevant software?

Hide your google profile avatar, sign up for a datum account and view the default assigned avatar image (a robot); make your avatar public, log back into datum, the robot image is not changed to be the user's avatar

What is the expected behavior?

Every time I change my github or google avatar image, I see that same image when I log into Datum