bug: (client sdks) 204 responses fail validation with --enable-runtime-response-validation

[mnahkies]

clients generated with --enable-runtime-response-validation try to validate empty responses, such as a 204 as being undefined, eg: z.undefined().

unfortunately axios actually returns an empty string "" instead of undefined, and thus the runtime validation fails, whilst fetch chokes on SyntaxError: Unexpected end of JSON input when calling .json()

Workarounds

• For axios we can workaround by using a response interceptor for axios that converts "" to undefined
• For fetch we should simply not call json() if the status code is 204