Executing the OAuth 2 provider connection workflow

In order to save the provider details, we need to fetch the available details from the provider, available via the OAuth 2 connection. Next, we create a CalendarUser table from the available details. Note that we need to create at least one GrantedAuthority role. Here, we have used CalendarUserAuthorityUtils#createAuthorities to create ROLE_USERGrantedAuthority:

    //src/main/java/com/packtpub/springsecurity/authentication/
    ProviderConnectionSignup.java

    @Service
    public class ProviderConnectionSignup implements ConnectionSignUp {
         ...
    @Override
    public String execute(Connection<?> connection) {
        UserProfile profile = connection.fetchUserProfile();
        CalendarUser user = new CalendarUser();
        if(profile.getEmail() != null){
             user.setEmail(profile.getEmail());
          }
        else if(profile.getUsername() != null){
             user.setEmail(profile.getUsername());
       ...