Support Watch

[roycaihw]

We should support watch calls to meet Silver Requirements once swagger-codegen supports:

• Streaming responses in go client. Ref: [Go] Support streaming responses in go client swagger-api/swagger-codegen#8199

/assign

[brendandburns]

@roycaihw We're moving to openapi-generator, can you move the PR to that project:

https://github.com/OpenAPITools/openapi-generator

[brendandburns]

And actually I implemented this in #24