Add feature for writing Java `null` Strings as `""`, write null `java.util.Collection` or array as `[]`

Hi Jackson community!

Our front-end colleague do not want to get null from back-end, and I tried to overwrite some kinds of null as default values. Here are 3 kinds of them: String, Collection and array. And I have tried some approaches, like setNullSerializer, overwrite CollectionSerializer, but not fits well.

Another way to achieve this is using reflection to replace a default value to null properties before serialization, but I don't prefer this because it would reduce server performance.

It seems to be a common requirement. So it would be great if jackson supports this feature.