Consider renaming `o.s.b.jackson2.Json*` classes to `Jackson2*`

[vpavic]

In the early days with Spring Boot 4, projects that rely on Jackson a lot will likely have to use Jackson 3 and Jackson 2 annotations side by side, until the broader ecosystem moves to Jackson 3. For example:

@JacksonMixin(ThirdPartyClass.class)
@JsonMixin(ThirdPartyClass.class)
@JsonIgnoreType
class ThirdPartyClassMixin {

}

To improve readability and consistency, perhaps annotations like @JsonMixin (or basically all classes under org.springframework.boot.jackson2) could be renamed to @Jackson2Mixin. That isn't a new breaking change (vs Spring Boot 3) since those classes have either way already been relocated.

[wilkinsona]

Thanks for the suggestion. We considered this but decided against it as we wanted an upgrade where you want to continue to use Jackson 2 to be a matter of updating imports and nothing more. However, I don't think we'd considered the possibility of both annotations being used at the same time on one mixin class as shown above. We'll discuss it again with that in mind.