Switch to Postgresql

[vermegi]

This is an ask from Sonja Gu and supported by Asir. Since there is a strong drive for Postgresql this fiscal for the sales teams, they would prefer a switch from MySQL as a database to Postgresql.
I am not sure how big this effort would be, but what we need to take into account if we switch this:

• code changes: dependency switch in pom files + double check all config files
• step changes in lab 2: https://azure-samples.github.io/java-microservices-aca-lab/docs/02_lab_migrate/0203.html
• step changes in lab 4: https://azure-samples.github.io/java-microservices-aca-lab/docs/04_lab_secrets/04_openlab_secrets_aca.html
• step changes in lab 6: https://azure-samples.github.io/java-microservices-aca-lab/docs/06_lab_private/0601.html
• template changes in lab 7: https://github.com/Azure-Samples/java-microservices-aca-lab/tree/main/infra/bicep/modules/database

• a full retest of the lab steps.