Support Jackson 3.x

[bedrin]

Migration guide described here: https://github.com/FasterXML/jackson/wiki/Jackson-Release-3.0

[CarstenWickner]

Hi @bedrin,

Thanks for raising this.
I'll look into it in the foreseeable future, which will likely involve a major version bump for me as well.
As I don't want to maintain parallel versions, I will see what other pending topics I can resolve first, before taking this step, though.
The actual migration guide appears to be still in progress, but it looks to be manageable so far.