This project is being implemented as a project that includes all the spring microservices, cloud, messaging systems that I have learned about.

Project is done .

Invoice Service Generate PDF -> Samples Output ->

Mail Service Sending Basic Mail -> Samples Output ->

What technologies exist ?

Integration Tests with TestContainers And JUnit5 
Gateway Service With Spring Cloud Gateway
Auth Server with Keycloak
NoSQL Database ( Apache Cassandra )
Relational Database ( PostgreSQL)
Messaging Systems (Kafka)
Redis Cache 
Resilience pattern with Resilience4J 
Eureka registry service
Config server with git repository
Zipkin for distributed tracing
ELK (Elasticsearch , Logstash , Kibana) Stack for distributed logging
Statistic service with Async communication -> Kafka
Exception Handling
Layered Architecture
Dockerize all project ( maybe not implementing )