* Fix nullable support in go-experimental client
* Fix support for models with parents and container fields
* Make sure that oneOf interfaces serialize properly even if they're required (non-pointers) on other models
* Spaces => tabs
* Regenerate samples
* Make some methods of nullables pointer-receivers, add tests
* Improve the Get/Set logic to make usage more convenient
* Address review
* [go-experimental] export required fields without pointer, only omitempty if type is not required and not nullable
* fix: go-experimental sample code
* fix: export nullable field as pointer
* update samples
* feat: nullable types
* add getter/setter for required fields, improve docstring
* [Go][experimental-client] Properly define packageName for go-experimental sample client
* [Go][experimental-client] make structure members pointers, provide custom marshalling.
