Help users to easily revoke access to the service

[choco-latin]

In terms of rights given, at the end of the process I had to go on my whatsapp parameters and google account parameters to revoke access to the app. I think that it would be nice that, at the end of the process, the webpage propose a couple of buttons to revoke the access (should be optional in case people want to regularly update their pictures)(I have no idea if this is technically possible).

Since this surely requires some decent amount of work, a temporary fix could be to provide instructions in a few lines, or a link redirecting to some tutorial

[guyzyl]

I now notice that I never commented on this (sorry).
@choco-latin this sounds like a great idea, you're welcome to open a PR for this (or I might get around to it sometime in the future).