Add new file

doc/api/lease6-wipe.json

+{
+    "name": "lease6-wipe",
+    "brief": "lease6-wipe is designed to remove all leases associated with a given subnet.",
+    "description": "See <xref linkend=\"lease6-wipe\"/>",
+    "support": [ "kea-dhcp4", "kea-dhcp6" ],
+    "avail": "1.3.0",
+    "hook": "lease_cmds",
+    "cmd-syntax": "{
+  \"command\": \"lease6-wipe\",
+  \"arguments\": {
+    \"subnet-id\": 66
+  }
+}",
+    "cmd-comment": "Note: not all backends support this command.",
+}
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