Add ObjectMapper in FunctionCallbackWrapper constructor

[alexcheng1982]

FunctionCallbackWrapper has a Builder object to build FunctionCallbackWrappers. The Builder has a method withObjectMapper to pass in custom ObjectMappers. However, this custom ObjectMapper is not used in the constructor of FunctionCallbackWrapper, so FunctionCallbackWrapper always uses the default ObjectMapper.

new ObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)

This causes problems when using Kotlin data classes as the function types. For serialization/deserialization with Kotlin data classes, the KotlinModule should be registered to the ObjectMapper, which requires a custom ObjectMapper. The workaround is using records.

In this fix, I added the ObjectMapper to the constructor of FunctionCallbackWrapper. No null-check is required as this constructor is private and Builder is the only way to create new instances of FunctionCallbackWrapper. Null-check is already done in the build method of Builder. The default value of ObjectMapper is the same as before, which is also already defined in Builder.

[tzolov]

Thanks for the improvement @alexcheng1982

[tzolov]

Rebased, squashed and merged at 0a3a202

in addition to the original commit make the default object mapper match the config of the ModelOptionsUtil.