[dart] Fix api client deserialization for json_serializable

[agilob]

Oh boy I hope this works

It works

@kuhnroyal

[agilob]

I think this is too much of a change and should be more conditional for now... brb

[agilob]

Class.fromJson is only used in json_serializable not for native

[agilob]

@kuhnroyal bump

[kuhnroyal]

Fine by me

[agilob]

Failure in:

[SEVERE] built_value_generator:built_value on lib/model/enum_arrays.dart:
An error `FormatterException` occurred while formatting the generated source for
  `package:openapi/model/enum_arrays.dart`
which was output to
  `lib/model/enum_arrays.built_value.g.part`.
This may indicate an issue in the generator, the input source code, or in the
source formatter.
Could not format because the source could not be parsed:

line 43, column 5: Expected an identifier.
   ╷
43 │ '\\$': 'dollar',
   │     ^
   ╵
line 39, column 15: Expected an identifier.
   ╷
39 │ 'dollar': '\\$',
   │               ^

[kuhnroyal]

Ya, #8947 fixed this on master. Just needs a rebuild probably.

[agilob]

Yup, passed now after pulling master