authorize {
                uri = "${..connect_uri}/authorize"
                method = "post"
                body = "json"
        }

The console output is :

Ready to process requests
rad_recv: Access-Request packet from host 192.168.118.102 port 44655, id=9, length=94
    User-Name = '4448'
    CHAP-Password = 0x4b29d9af0b3c3097abb01df83dd6bd2559(0) # Executing section authorize from file /usr/local/etc/raddb/sites-enabled/default
(0)   authorize {
(0)   [preprocess] = ok
(0) chap : Setting 'Auth-Type := CHAP'
(0)   [chap] = ok
(0)   [mschap] = noop
(0) eap : No EAP-Message, not doing EAP
(0)   [eap] = noop
rlm_rest (rest): Reserved connection (2)
(0) rest : Expanding URI components
(0) rest : EXPAND http://192.168.113.151:2233
(0) rest :    --> http://192.168.113.151:2233
(0) rest : EXPAND /authorize
(0) rest :    --> /authorize
(0) rest : Sending HTTP POST to "http://192.168.113.151:2233/authorize"
(0) rest : Encoding attribute "User-Name"
(0) rest : Encoding attribute "CHAP-Password"
(0) rest : Encoding attribute "NAS-IP-Address"
(0) rest : Encoding attribute "Calling-Station-Id"
(0) rest : Encoding attribute "CHAP-Challenge"
(0) rest : Encoding attribute "NAS-Port-Id"
(0) rest : Processing response header
(0) rest :     Status : 400 (Bad Request)
(0) rest :     Type   : json (application/json)
rlm_rest (rest): Released connection (2)
(0)   [rest] = invalid
(0)  } #  authorize = invalid
(0) Using Post-Auth-Type Reject

If I do a curl POST request to that URI it works.  No traffic coming from the server I've checked with tcpdump.