Adding new features and refactoring

[uPagge]

Hi, first of all thank you very much for this project, it helped a lot on our project :)

But unfortunately, everything was not as smooth as we would like, so the plugin had to be updated. I open the pull request because I hope that these are useful changes.

For reference, we use our own oauth2 server in our project

Refactoring This mainly affected the creation and updating of entities and groups. I Packed everything in a DTO class for convenience. I also expanded the number of fields that can be obtained from the SSO server

New features There is a new field in the settings, the user exit token. Why is it needed? We needed this when it was necessary to make a simultaneous exit in all SSO-related applications. In other words, if a user logs out of app A, then they must also log out of app B, which is lifray.

In order for the SSO server to log out any user to liferay, it calls the /portal/logout method with the ServiceAuth header, which is set in the settings, and the request parameter of the user's UUID in liferay

For more information about the implementation, see LibFilter#processFilter.