Upgrade to SpringBoot 4

[brunotrodrigues]

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Migration to Spring Boot 4 need a lot of other libraries to update as well. These are the most important ones:

• JDK25
• Spring Boot 4
• Spring Framework 7
• HttpClient 5
• Jackson 3
• Jakarta (JEE) 11
• Junit 6
• Groovy 5
• XML Unit 2.0 (instead of XML Unit 2.0 legacy)
• Hibernate 7

[skin27]

Change the milestone to 6.0.0

[skin27]

Additionally to upgrading the dependencies a code review (mainly custom-components):

• Move to latest Java Standards
• Improve readability and maintainability
• Update deprecated methods to new ones