middleware: add a registration model

example_config.yaml

@@ -121,21 +121,21 @@ chihaya:
   # response has been returned to a BitTorrent client.
   prehooks:
   #- name: jwt
-  #  config:
+  #  options:
   #    issuer: "https://issuer.com"
   #    audience: "https://chihaya.issuer.com"
   #    jwk_set_url: "https://issuer.com/keys"
   #    jwk_set_update_interval: 5m
 
   #- name: client approval
-  #  config:
+  #  options:
   #    whitelist:
   #    - "OP1011"
   #    blacklist:
   #    - "OP1012"
 
   #- name: interval variation
-  #  config:
+  #  options:
   #    modify_response_probability: 0.2
   #    max_increase_delta: 60
   #    modify_min_interval: true