     (json array, optional) A list of strings
         "str",                (string) client side supported feature, 'longpoll', 'coinbasevalue', 'proposal', 'serverlist', 'workid'
         ...
       ],
       "rules": [              (json array, required) A list of strings
         "segwit",             (string, required) (literal) indicates client side segwit support
         "str",                (string) other client side supported softfork deployment
         ...
       ],
       "longpollid": "str", 