introduce WG_DEFAULT_ADDRESS_RANGE (CIDR notation)

This PR allows the use of Address Ranges using the CIDR notation.

To make it backward compatible, i introduced a new env variable WG_DEFAULT_ADDRESS_RANGE (defaults to the previous default of 24).

This allows the usage of smaller subnets (or possibly larger; but i didn't test that due to restrictions on my network). Client IPs will be calculated with correct IP addresses instead of making assumptions of the address space.

src/package-lock.json

@@ -13,6 +13,7 @@
         "debug": "^4.3.4",
         "express": "^4.18.3",
         "express-session": "^1.18.0",
+        "ip": "^1.1.8",
         "qrcode": "^1.5.3",
         "uuid": "^9.0.1"
       },
@@ -2793,6 +2794,11 @@
         "node": ">= 0.4"
       }
     },
+    "node_modules/ip": {
+      "version": "1.1.8",
+      "resolved": "https://registry.npmjs.org/ip/-/ip-1.1.8.tgz",
+      "integrity": "sha512-PuExPYUiu6qMBQb4l06ecm6T6ujzhmh+MeJcW9wa89PoAz5pvd4zPgN5WJV104mb6S2T1AwNIAaB70JNrLQWhg=="
+    },
     "node_modules/ipaddr.js": {
       "version": "1.9.1",
       "resolved": "https://registry.npmjs.org/ipaddr.js/-/ipaddr.js-1.9.1.tgz",