title: Firebase Auth - get provider ID
body: <p>I'm using the following code, to detect auth provider and log out properly</p>
  
  <pre><code>static func logOut() {
      let auth = FIRAuth.auth()!
      let provider = auth.currentUser?.providerID
      switch provider! {
          case "Facebook": FBSDKLoginManager().logOut()
          case "Google": GIDSignIn.sharedInstance().signOut()
          case "Twitter": Twitter.sharedInstance().sessionStore.logOutUserID(TWTRAPIClient.withCurrentUser().userID!)
          default:
              print("Unknown provider ID: \(provider!)")
              return
      }
      try! auth.signOut()
  }
  </code></pre>
  
  <p>But the provider is always "Firebase". What am I doing wrong? 0_o Once that code throw "Facebook" when I was logged in twitter. Thanks in advance</p>
  
  <p>UPD: Yeah, I actually can store auth provider in <code>UserDefaults</code>, but maybe it's Firebase bug. I'm using Firebase SDK 3.5.2 </p>