Upgrade SCXA to use SpringBoot

[ke4]

We need to modernise our applications. We are currently generating a WAR file and deploying it to a Tomcat server in a VM.
This is a very outdated way to deploy and execute an application and we have so many issues with Tomcat, like disappearing WAR and config files, disappearing Tomcat manager app, etc...
Instead of the above we could just deploy a fat JAR file with an embedded web server (Tomcat, Jetty or else) to the same VM and execute the JAR file.
Currently we are using Sprint Framework version: 5.1.5. We could migrate it to the latest Spring Boot version and configure the gradle script to be able to deploy the JAR file automatically when we have a successful build.

Here is a guide with some suggestions how to do the migration: https://www.baeldung.com/spring-boot-migration

The following task should be done before starting this one: Upgrade Spring Framework to the latest one in SCXA