Spring-boot sample app

Following functionlaities are demonstrated

1. CRUD operations
2. Persist to H2 (JPA, QueryDSL)
3. Authn and Authz using beaer token with keycloak
4. Keycloak customization to import realm and preconfigure it
5. BDDs with Cucumber and TestNG
6. maven, docker and docker-compose
7. API documentation with open-api 3