in src/main/java/org/jetbrains/teamcity/githubauth/GitHubOAuth.java [58:65]
public String getUserRedirect(HttpServletRequest request) {
OAuthConnectionDescriptor connection = getSuitableConnection();
HttpSession session = request.getSession();
String state = StringUtil.generateUniqueHash();
session.setAttribute(STATE_SESSION_ATTR_NAME, state);
return gitHubOAuthClient.getUserRedirect(connection.getParameters().get(GitHubConstants.CLIENT_ID_PARAM), DEFAULT_SCOPE,
buildRedirectUrl(), state);
}