OAuth2 UserInfo factory

[webcane]

implement factory pattern for OAuth2UserInfoFactory class.

[webcane]

userInfoMap holds OAuth2UserInfoProvider. for example: GithubUserInfoProvider. He creates github UserInfo instance.

  @Override
  public UserInfo getUserInfo(Map<String, Object> attributes) {
    return new GithubOAuth2UserInfo(attributes);
  }

[webcane]

each concrete UserInfo instance knows how to extract id, name, email and imageUrl from the particular OAuth2 attributes. example: GithubOAuth2UserInfo