[#10,!3] reservation-get/del/all references updated.

doc/api/reservation-add.json

@@ -5,7 +5,8 @@
         the client will be assigned to, DHCPv4 and DHCPv6 options and
         more.",
     "support": [ "kea-dhcp4", "kea-dhcp6" ],
-    "avail": "1.2.0, host_cmds library (premium)",
+    "hook": "host_cmds",
+    "avail": "1.2.0",
     "description": "See <xref linkend=\"cmd-reservation-add\"/>",
 
     "cmd-syntax": "{

doc/api/reservation-del.json

@@ -2,7 +2,8 @@
     "name": "reservation-del",
     "brief": "Deletes an existing host reservation.",
     "support": [ "kea-dhcp4", "kea-dhcp6" ],
-    "avail": "1.2.0, host_cmds library (premium)",
+    "hook": "host_cmds",
+    "avail": "1.2.0",
 
     "cmd-syntax": "{
     \"command\": \"reservation-del\",

doc/api/reservation-get.json

@@ -2,7 +2,8 @@
     "name": "reservation-get",
     "brief": "attempts to retrieve an existing host reservation",
     "support": [ "kea-dhcp4", "kea-dhcp6" ],
-    "avail": "1.2.0, host_cmds library (premium)",
+    "hook": "host_cmds",
+    "avail": "1.2.0",
 
     "cmd-syntax": "{
     \"command\": \"reservation-get\",