kea: add DHCP4 HA config (hot-standby)

roles/kea/templates/kea/kea-dhcp4.conf.j2

@@ -10,6 +10,39 @@
         "socket-name": "/run/kea/kea4-ctrl-socket"
     },
 
+    "hooks-libraries": [
+        {
+            "library": "/usr/lib/x86_64-linux-gnu/kea/hooks/libdhcp_lease_cmds.so"
+        },
+
+        {
+            "library": "/usr/lib/x86_64-linux-gnu/kea/hooks/libdhcp_ha.so",
+            "parameters": {
+                "high-availability": [ {
+                    "this-server-name": "{{ inventory_hostname.split('.')[0] }}",
+                    "mode": "hot-standby",
+                    "heartbeat-delay": 10000,
+                    "max-response-delay": 60000,
+                    "max-ack-delay": 5000,
+                    "max-unacked-clients": 5,
+                    "sync-timeout": 60000,
+                    "peers": [
+                        {
+                            "name": "{{ lookup('dig', dhcpd_primary+'/PTR').split('.')[0] }}",
+                            "url": "http://{{ dhcpd_primary }}:8000/",
+                            "role": "primary"
+                        },
+                        {
+                            "name": "{{ lookup('dig', dhcpd_secondary+'/PTR').split('.')[0] }}",
+                            "url": "http://{{ dhcpd_secondary }}:8000/",
+                            "role": "standby"
+                        }
+                    ]
+                } ]
+            }
+        }
+    ],
+
     "lease-database": {
         "type": "memfile",
         "lfc-interval": 3600