Pull request 2254: 4923 gopacket DHCP vol.9

Updates #4923.

Squashed commit of the following:

commit 05322419156d18502f3f937e789df02d78971b30
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Jul 9 18:18:35 2024 +0300

    dhcpsvc: imp docs

commit 083da3671320f7774db9c5b854e663162da9d214
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Tue Jul 9 15:28:52 2024 +0300

    dhcpsvc: imp code, tests

commit 22e37e587e29c781abd4f2486f282dcfbffb4e6b
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Jul 8 19:31:43 2024 +0300

    dhcpsvc: imp tests

commit 83ec7c54ef1e689a1f887e78e3055522539222d5
Author: Eugene Burkov <E.Burkov@AdGuard.COM>
Date:   Mon Jul 8 18:56:21 2024 +0300

    dhcpsvc: add db

internal/dhcpsvc/testdata/TestServer_Leases/leases.json

@@ -0,0 +1,15 @@
+{
+    "leases":  [{
+        "expires": "2042-01-02T03:04:05Z",
+        "ip": "192.168.0.3",
+        "hostname": "example.host",
+        "mac": "AA:AA:AA:AA:AA:AA",
+        "static": false
+    }, {
+        "ip": "192.168.0.4",
+        "hostname": "example.static.host",
+        "mac": "BB:BB:BB:BB:BB:BB",
+        "static": true
+    }],
+    "version": 1
+}