FIX: when associating Github account disassociate others

There are some cases where an email floats from one GitHub account to another
if this happens just take over the Github mapping record

lib/auth/github_authenticator.rb

@@ -86,7 +86,12 @@ class Auth::GithubAuthenticator < Auth::Authenticator
         if !!candidate[:verified] && (user = User.find_by_email(candidate[:email]))
           result.email = candidate[:email]
           result.email_valid = !!candidate[:verified]
-          GithubUserInfo.create(
+
+          GithubUserInfo
+            .where('user_id = ? OR github_user_id = ?', user.id, github_user_id)
+            .destroy_all
+
+          GithubUserInfo.create!(
               user_id: user.id,
               screen_name: screen_name,
               github_user_id: github_user_id