pom.xml miss configured and at the wrong directory in v2.1.1.zip

[dwolf42]

The file was in the app directory, should be placed in the main directory.

Also in the pom itself the maven-compiler-plugin seems miss configured, as far as I can tell.
I had to comment the plugins (line 140 -155) in order to make the project build in the pipeline.

Even refactoring it like this didn't help
```

org.springframework.boot
spring-boot-maven-plugin
${spring-boot.version}


org.apache.maven.plugins
maven-compiler-plugin

true
lines,vars,source

-g:source,lines,vars