What is the best way to add social media login and registration to a site with an existing user base?

Question

Yii

Good afternoon.
The situation is as follows: there is a site written in the Yii framework, which is used by about 2,000 people. All of them are registered on the site by email, each has a username / password.
Task: add the ability to log in or register on the site through facebook/vk/twitter and other services, while also retaining the traditional method of authorization and registration. The plug-in for these purposes is found and studied, but there is a problem of interaction with users.
And the problem is this: the audience of the site is mostly technically illiterate people and it is very likely that when they see a new authorization method, instead of entering the username and password as before, they will think "Oh, I'll enter through the contact - it's more convenient !" and instead of entering the site they will create for themselvesa new account, and they will pester support with questions like "I'm logged in, where did my data go?", "Restore my profile," etc. It's
useless to post explanatory signs - we know that users almost never read warnings.
In this case, what is the best way to add a new authorization method, and ensure that users do not get stupid and start creating new accounts for themselves?

Answer 1

Save the authorization method and, for example, your mail in encrypted form in cookies. When registering through social networks, check how a person used to enter. If it turns out that he used the usual authorization, then ask for the password from the account and combine them. So the person will have 2 authorization options and 1 account.

Answer 2

when a user logs in through VK for the first time, the first thing to do is to ask him if he has an old account and if there is, glue them together, and if not, then a new record is created. make the question box as visible as possible, maybe make a separate page or so for this

Answer 3

You can add account management to the profile, where users themselves can add their accounts from social networks. Plus, to implement for support the ability to quickly link a social account to an account from your database for cases of registering a "new" user.