feat(config): update database credentials to use environment variables

Author: Theo-lbg

src/main/resources/application.properties

@@ -5,5 +5,5 @@ springdoc.swagger-ui.path=/api
 randomuser.api.base-url=https://randomuser.me/
 
 spring.datasource.url=jdbc:postgresql://localhost:5432/xpeho_db
-spring.datasource.username=postgres
-spring.datasource.password=postgres
+spring.datasource.username=${DB_USER}
+spring.datasource.password=${DB_PASSWORD}