Sample project showing problem with configuration properties exception

UPD: it is fixed with boot 2.2.0.RELEASE. See spring-projects/spring-boot#18509 for details

By default application would show the problem

Extra tests

Open com.example.conversionproblem.AppProperties and uncomment second field:

@Valid
private Map<MyEnum, NestedProperty> myEnumMap;

to see that message would change

What else

There are 2 more spring profiles that show options with different behaviour:

1. good - it proofs that when there is no validation issues, context is created fine
2. enum - it proofs that for more simple scenario - explicit enum typing of keys spring generates expected validation message