[Maintenance] Leverage Spring 3.4 Features

[devtobi]

Relevant component

refarch-gateway, refarch-integrations

Problem description (optional)

No response

Desired solution

Spring Boot 3.4.0 got some new exciting features we could investigate to simplify some things and get rid of boilerplate code, e.g.:

• Structured Logging (Logstash Support built-in, might be able to remove custom configuration)
• Support in Testcontainers for Hazelcast
• Improved Observability with Application Groups

Keep in mind this issue also affects https://github.com/it-at-m/refarch-templates.

Considered alternatives (optional)

No response

Additional context (optional)

Take a look at https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-3.4-Release-Notes for more information

No duplicate

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