Fix Sonarqube dependency to postgres database

[profotoce59]

The content tests (contextLoads) are not successful when PostgreSQL is not available locally (for CI)

[profotoce59]

To fix failing contextLoads tests when PostgreSQL is not available (especially in CI), we implemented the following:

Added H2 test dependency in [pom.xml]
Kept test profile usage with @activeprofiles("test") in SpringBootJavaRandomUserApplicationTests.
Updated Sonar GitHub Actions workflow to:
generate [application-test.properties] from APPLICATION_TEST_PROPERTIES secret,

New secret has been added to the GitHub secret : APPLICATION_TEST_PROPERTIES
spring.datasource.url=jdbc:h2:mem:testdb;MODE=PostgreSQL;DB_CLOSE_DELAY=-1;DB_CLOSE_ON_EXIT=FALSE
spring.datasource.driver-class-name=org.h2.Driver
spring.datasource.username=<any_username>
spring.datasource.password=
spring.sql.init.mode=never