Upgrade to Spring Boot 2.2

Spring Boot 2.2 has just been released:

• https://spring.io/blog/2019/10/16/spring-boot-2-2-0
• https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.2-Release-Notes

One of the most important and impactful changes are related to Jakarta EE dependencies:

Where possible, we have moved from Java EE dependencies with a javax.** group ID to the equivalent Jakarta EE dependencies with a jakarta. group ID in Spring Boot’s starters. Dependency management for the Jakarta EE API dependencies has been added alongside the existing dependency management for the Java EE API dependencies. The dependency management for the Java EE API dependencies will be removed in the future and all users are encouraged to move to the Jakarta EE API dependencies.

As part of the Java EE to Jakarta EE migration, two dependencies have changed artifact ID in their latest maintenance releases. com.sun.mail:javax.mail is now com.sun.mail:jakarta.mail and org.glassfish:javax.el is now org.glassfish:jakarta.el. In the unlikely event that you were using either of these dependencies directly, please update your pom.xml or build.gradle accordingly.