Don't manually construct an `ObjectMapper`
As we'll find when setting up the ?, we will hit 0 due to our custom
ObjectMapper
which does not pick up the automagic configuration
provided through Spring Boot.
However, it's not as simple as removing the Bean definition, as then a
YAMLMapper
gets picked up, so we need to make sure we import the
JacksonAutoConfiguration
class to ensure the bean is created and
wired in.