Update Spring from 5.2.10.RELEASE to 5.2.15.RELEASE to fix CVE

CVE-2021-22118 has been fixed in version 5.2.15.RELEASE.
Doing the update allow to avoid build failure related to org.owasp:dependency-check-maven.

Update dependency-check to fix NullPointerException

Update dependency-check to version 6.1.6 to fix NullPointerException. See details: https://github.com/jeremylong/DependencyCheck/issues/3360

- Migrated to Java 11, JAXB 2.3.3 (Jakarta XML Binding), Apache CXF 3.4.1, Spring Boot Starter 2.3.5, Jakarta WS API 2.1.6
- Added junit under dependency management
- Replaced obsolete maven plugin 'findbugs' with 'spotbugs'
- Migrated OWASP dependency check maven plugin to 6.0.3
- Added unit test for unmarshalling/marshalling XACML document
- Updated license headers to 2021

- Upgraded plugin dependency-check to 5.3.2