Upgrade to Spring Boot 3.x/ Spring 6
To sum up, Spring Boot 2.7 has reached EOL (24 Nov 2023), and vulnerabilities have started to accumulate without expected fixes. As Spring 5 is not compatible with Spring Boot 3, we need to migrate both. The Spring 5 to 6 upgrade introduces a significant breaking change — the Javax to Jakarta migration.
Done in this MR !13 (merged)