Create interfaces for services managers

Problem/Motivation

Social Auth implementers are now storing tokens to allow external modules to access more data. However, they way to retrieve them from different social networks differs which makes it confusing.

For reference, follow #2857170: Remove access token session variables if login fails, #2857305: Save access token to allow external modules to request more data, and #2857106: Get the URL to user social page

Proposed resolution

Create interfaces for different authentication methods.

As an example, Google and Facebook implementers use OAuth 2, so we can create an interface which should be use in FacebookAuthManager and GoogleAuthManager.

Remaining tasks

• Write interface for OAuth2
• Determine more authentication methods which might need an interface

API changes

External methods will need to change the way they access data.

Example for OAuth2

/* @var \Google_Client $client */
$client = $this->networkManager->createInstance('social_auth_google')->getSdk();

$this->googleManager->setClient($client)
    ->setAccessToken($this->session->get('social_auth_google_access_token'))
    ->authenticate()

$user = $this->googleManager->getUserInfo();