Add env vars to app properties file

src/main/resources/application.properties

@@ -1,6 +1,6 @@
-spring.datasource.url=jdbc:postgresql://localhost:5432/plantsforyou
-spring.datasource.username=postgres
-spring.datasource.password=1234
+spring.datasource.url=jdbc:${DATABASE_URL}
+spring.datasource.username=${DATABASE_USERNAME}
+spring.datasource.password=${DATABASE_PASSWORD}
 spring.jpa.hibernate.ddl-auto=create-drop
 spring.jpa.show-sql=true
 spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.PostgreSQLDialect