Clarify that GsonBuilder.registerTypeAdapter makes JsonSerializer and JsonDeserializer null-safe #1697
Description
When calling GsonBuilder.registerTypeAdapter with a JsonSerializer or JsonDeserializer, it is made null-safe (see TreeTypeAdapter), i.e. the (de-)serializer will not be consulted when a null value is handled.
It appears this is currently not documented.
It should be documented in registerTypeAdapter and it should refer to TypeAdapter as alternative which does allow handling null-values.