* add custom gson deserializer
* add check for additional fields, required fields
* add tests for custom deserializer
* add custom adapter
* add custom adapter
* register type adapter factory
* comment out custom deserializer and use adapter instead
* add okhttp-gson-nextgen
* add new files
* restore okhttp-gson
* switch to adapter
* remove custom de/serializer
* add comment
* update tests
* test nextgen in ci
* update doc
* use full model name in JSON.java
* undo changes
* add oneof discriminator support
* fix anyOf
* remove mappings
* add more tests
* fix oneof deserialization, add more tests
* add error body and type to api exception class
* JSON to use instance variables/methods
* Revert "add error body and type to api exception class"
This reverts commit 07f34e2c450ad9f808b728173018b1e4d8fed458.
