Add user management

[M123-dev]

What

Add the functionality to login and register inside Smoothie

• Let users log into Smoothie #700
• Implement Open Food Facts contribution signup inside Smoothie #702
• Implement password reset inside Smoothie #701

Also add the user parameters to contributions

Documentation:
https://github.com/openfoodfacts/openfoodfacts-dart/blob/master/DOCUMENTATION.md#check-login-data
https://github.com/openfoodfacts/openfoodfacts-dart/blob/master/DOCUMENTATION.md#register-a-new-user

Blocked on

• Add support for user creation openfoodfacts-dart#171
• Login via the auth.pl api openfoodfacts-dart#167
• Add support for password reset openfoodfacts-dart#215

Part of

• 🎯 What can I work on ? #525

[monsieurtanuki]

@stephanegigandet What is the scope of this issue:

1. what happens if the end-user does not register? read-only access with the default user?
2. what happens if the end-user does register? all read/write accesses with the registered user only, or are there still actions with the default user?
3. the log in should probably be part of the onboarding, shouldn't it?

[teolemon]

• @M123-dev I added support for password reset to the issue.
• @monsieurtanuki historically, we allowed anonymous new product addition. We could also allow photo upload without much risk. Finally, we added Anonymous UUID for those cases in the classic apps.
• If the user is logged in, all WRITE actions with the user (edit / img upload…). READ action do not need to be authed.
• On the classic apps, it's not part of the onboarding. If we can make it work as part of onboarding, why not ? A simplistic implementation in settings would already be great.

[M123-dev]

Thanks a lot for your contribution on signup @monsieurtanuki, looks like we are done here

[monsieurtanuki]

@M123-dev I guess there are still tests and UX fine-tunings to do here but you're right, basically we're done.