Support Jackson 3

[lbenedetto]

The latest version of Spring is migrating to Jackson 3.
The new Jackson version is aggressively NOT backwards compatible with Jackson 2.

Not migrating will certainly cause problems for anyone trying to use the latest Spring version.

However, I've taken a look through your code and migrating is pretty simple.

The new configuration for a strict mapper in DataHandler would look like this in order to pass the tests

JsonMapper.builder()
        .propertyNamingStrategy(PropertyNamingStrategies.UPPER_CAMEL_CASE)
        .enable(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES)
        .changeDefaultPropertyInclusion(incl -> incl.withValueInclusion(JsonInclude.Include.NON_NULL))
        .enable(DeserializationFeature.FAIL_ON_IGNORED_PROPERTIES)
        .enable(DeserializationFeature.FAIL_ON_MISSING_CREATOR_PROPERTIES)
        .enable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
        .build();