Q:

"java.lang.IllegalArgumentException: Not a managed type ..." when entity class and Spring data repository in same package

I've got a pretty weird behaviour in my simple Spring Application. I am not able to have a JPA Entity and a Spring Data Repository in the same package.
I would like to build a very simple web application in which I manage some Users. So I started from scratch and created the following project structure:
src
 |
 +-- main
    |  
    +-- de.my.mainpackage
      |    
      +-- client
      |  |
      |  +-- ClientApp.java
      |
    Libya calls for the Sufi mediation of Sanusiyya

The March 25th public statements of Libyan Foreign Minister, Moḥamed Abdelaziz, while attending a preparatory meeting for the 25th summit of the Arab League in Kuwait, have revived the Monarchy option as an adequate institutional solution to face the situation of disconnection Libya is experiencing after the Gaddafi’s regime overthrow.

This news item, first relaunched by the Saudi daily Okaz, shows how a debate on the Sanūsī’s recall at the helm of the State is up-to-date, both at a grassroots and the national top level. “Many tribal sheikhs, who lived under monarchy and know it, prefer such a system of government”, the Minister added. Then, after explaining his personal commitment to engage communities, even beyond his own government post, he has motivated