update spring boot and Helmholtz AAI Domain name

Motivation:

New spring boot starter is out and it comes with better support for HAL and HAL-FORM that will be implementing.

Also, Helmholtz AAI domain name is change to reflect the lastest URIs.

Modification:

• update spring-boot-starter-parent to the latest release which is 2.3.0.RELEASE
• change the URIs of the oauth2
• move all the version number to the properties node of the pom file

Result:

No visible changes to users

Target: master Acked-by: Review: https://gitlab.hzdr.de/hifis-technical-platform/helmholtz-cerebrum/-/merge_requests/14