Support PostgreSQL backend for spring-petclinic-microservices

[selvasingh]

Let's mirror the approach taken at https://github.com/spring-projects/spring-petclinic/blob/main/src/main/resources/db/postgres/petclinic_db_setup_postgres.txt and add support for PostgreSQL backend for spring-petclinic-microservices and push those changes to the parent repo https://github.com/spring-petclinic/spring-petclinic-microservices