[#325] Authentication via Social Networks

[ruslankhaertdinov]

Related to: #325

Demo: https://auth-via-networks.herokuapp.com/

[ruslankhaertdinov]

@MaximLarionov I apply review comments and reopen PR into examples branch, please take a look again.

[maxinspace]

not really DRY to repeat one check in the every single action, WDYT about moving this check to callback before_action?

[ruslankhaertdinov]

Yep, agree.

[maxinspace]

Moreover, it appears that we partially can't use some social services for oauth.

There is 3 cases of oauth behavior:

1. Sign in user via finding SocialProfile by uid and provider from auth hash.
2. Sign in user via finding him by email from auth hash, and create SocialProfile for user.
3. Create new user via auth hash, and SocialProfile for him.

Usually, auth hash should contain some data, which says, that account from that Social Profile is confirmed/verified by email. But some services doesn't have that data, like LinkedIn or GitHub.
So we can't trust this auth hash data, and we can't use it for authenticating user in second case.

So it seems, that we have to develop strategy for those cases.

[ruslankhaertdinov]

@MaximLarionov please take a new look

[ruslankhaertdinov]

@timurvafin also kindly please review

[ruslankhaertdinov]

@MaximLarionov ping)

[maxinspace]

I guess, we should try to find social profile, before finding by email.

If user has already signed with this social account, then he should have Social Profile, so it's more reasonable to look for it, and if we haven't found one - find by email, and create new social profile for him.

[maxinspace]

@ruslankhaertdinov it seems like that's all from my side for current moment :)

[ruslankhaertdinov]

@MaximLarionov thanks a lot!)

[ruslankhaertdinov]

@MaximLarionov please take a look again, when you have time ;)